diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -39,13 +39,10 @@
 
   def testcase_authorization
     #admin always has privileged
-    puts "haha"
     if @current_user.admin?
       return true
     end
 
-    puts "hehe"
-    puts GraderConfiguration["right.view_testcase"]
     unauthorized_redirect unless GraderConfiguration["right.view_testcase"]
   end
 
@@ -61,27 +58,28 @@
       return false
     end
 
+
     # check if run in single user mode
     if GraderConfiguration[SINGLE_USER_MODE_CONF_KEY]
-      user = User.find_by_id(session[:user_id])
-      if user==nil or (not user.admin?)
+      if @current_user==nil or (not @current_user.admin?)
         flash[:notice] = 'You cannot log in at this time'
         redirect_to :controller => 'main', :action => 'login'
         return false
       end
-      unless user.enabled?
-        flash[:notice] = 'Your account is disabled'
-        redirect_to :controller => 'main', :action => 'login'
-        return false
-      end
       return true
     end
 
+    # check if the user is enabled
+    unless @current_user.enabled? or @current_user.admin?
+      flash[:notice] = 'Your account is disabled'
+      redirect_to :controller => 'main', :action => 'login'
+      return false
+    end
+
     if GraderConfiguration.multicontests? 
-      user = User.find(session[:user_id])
-      return true if user.admin?
+      return true if @current_user.admin?
       begin
-        if user.contest_stat(true).forced_logout
+        if @current_user.contest_stat(true).forced_logout
           flash[:notice] = 'You have been automatically logged out.'
           redirect_to :controller => 'main', :action => 'index'
         end
diff --git a/app/controllers/groups_controller.rb b/app/controllers/groups_controller.rb
new file mode 100644
--- /dev/null
+++ b/app/controllers/groups_controller.rb
@@ -0,0 +1,86 @@
+class GroupsController < ApplicationController
+  before_action :set_group, only: [:show, :edit, :update, :destroy,
+                                   :add_user, :remove_user,
+                                   :add_problem, :remove_problem,
+                                  ]
+  before_action :authenticate, :admin_authorization
+
+  # GET /groups
+  def index
+    @groups = Group.all
+  end
+
+  # GET /groups/1
+  def show
+  end
+
+  # GET /groups/new
+  def new
+    @group = Group.new
+  end
+
+  # GET /groups/1/edit
+  def edit
+  end
+
+  # POST /groups
+  def create
+    @group = Group.new(group_params)
+
+    if @group.save
+      redirect_to @group, notice: 'Group was successfully created.'
+    else
+      render :new
+    end
+  end
+
+  # PATCH/PUT /groups/1
+  def update
+    if @group.update(group_params)
+      redirect_to @group, notice: 'Group was successfully updated.'
+    else
+      render :edit
+    end
+  end
+
+  # DELETE /groups/1
+  def destroy
+    @group.destroy
+    redirect_to groups_url, notice: 'Group was successfully destroyed.'
+  end
+
+  def remove_user
+    user = User.find(params[:user_id])
+    @group.users.delete(user)
+    redirect_to group_path(@group), notice: "User #{user.login} was removed from the group #{@group.name}"
+  end
+
+  def add_user
+    user = User.find(params[:user_id])
+    @group.users << user
+    redirect_to group_path(@group), notice: "User #{user.login} was add to the group #{@group.name}"
+  end
+
+  def remove_problem
+    problem = Problem.find(params[:problem_id])
+    @group.problems.delete(problem)
+    redirect_to group_path(@group), notice: "Problem #{problem.name} was removed from the group #{@group.name}"
+  end
+
+  def add_problem
+    problem = Problem.find(params[:problem_id])
+    @group.problems << problem
+    redirect_to group_path(@group), notice: "Problem #{problem.name} was add to the group #{@group.name}"
+  end
+
+  private
+    # Use callbacks to share common setup or constraints between actions.
+    def set_group
+      @group = Group.find(params[:id])
+    end
+
+    # Only allow a trusted parameter "white list" through.
+    def group_params
+      params.require(:group).permit(:name, :description)
+    end
+end
diff --git a/app/controllers/problems_controller.rb b/app/controllers/problems_controller.rb
--- a/app/controllers/problems_controller.rb
+++ b/app/controllers/problems_controller.rb
@@ -195,6 +195,11 @@
       set_available(true)
     elsif params.has_key? 'disable_problem'
       set_available(false)
+    elsif params.has_key? 'add_group'
+      group = Group.find(params[:group_id])
+      get_problems_from_params.each do |p|
+        group.problems << p
+      end
     end
     redirect_to :action => 'manage'
   end
diff --git a/app/controllers/user_admin_controller.rb b/app/controllers/user_admin_controller.rb
--- a/app/controllers/user_admin_controller.rb
+++ b/app/controllers/user_admin_controller.rb
@@ -228,6 +228,7 @@
     end
   end
 
+
   # contest management
 
   def contests
@@ -423,6 +424,8 @@
       @action[:set_enable] = params[:enabled]
       @action[:enabled] = params[:enable] == "1"
       @action[:gen_password] = params[:gen_password]
+      @action[:add_group] = params[:add_group]
+      @action[:group_name] = params[:group_name]
     end
 
     if params[:commit] == "Perform"
@@ -437,6 +440,10 @@
           u.save
         end
       end
+      if @action[:add_group] and @action[:group_name]
+        @group = Group.find(@action[:group_name])
+        @users.each { |user|  @group.users << user }
+      end
     end
   end
 
diff --git a/app/helpers/groups_helper.rb b/app/helpers/groups_helper.rb
new file mode 100644
--- /dev/null
+++ b/app/helpers/groups_helper.rb
@@ -0,0 +1,2 @@
+module GroupsHelper
+end
diff --git a/app/models/grader_configuration.rb b/app/models/grader_configuration.rb
--- a/app/models/grader_configuration.rb
+++ b/app/models/grader_configuration.rb
@@ -12,6 +12,7 @@
   MULTIPLE_IP_LOGIN_KEY = 'right.multiple_ip_login'
   VIEW_TESTCASE = 'right.view_testcase'
   SINGLE_USER_KEY = 'system.single_user_mode'
+  SYSTEM_USE_PROBLEM_GROUP = 'system.use_problem_group'
 
   cattr_accessor :config_cache
   cattr_accessor :task_grading_info_cache
@@ -119,6 +120,10 @@
   def self.analysis_mode?
     return get(SYSTEM_MODE_CONF_KEY) == 'analysis'
   end
+
+  def self.use_problem_group?
+    return get(SYSTEM_USE_PROBLEM_GROUP)
+  end
   
   def self.contest_time_limit
     contest_time_str = GraderConfiguration[CONTEST_TIME_LIMIT_KEY]
diff --git a/app/models/group.rb b/app/models/group.rb
new file mode 100644
--- /dev/null
+++ b/app/models/group.rb
@@ -0,0 +1,5 @@
+class Group < ActiveRecord::Base
+  has_and_belongs_to_many :problems
+  has_and_belongs_to_many :users
+end
+
diff --git a/app/models/problem.rb b/app/models/problem.rb
--- a/app/models/problem.rb
+++ b/app/models/problem.rb
@@ -2,6 +2,7 @@
 
   belongs_to :description
   has_and_belongs_to_many :contests, :uniq => true
+  has_and_belongs_to_many :groups
   has_many :test_pairs, :dependent => :delete_all
   has_many :testcases, :dependent => :destroy
 
diff --git a/app/models/user.rb b/app/models/user.rb
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -7,6 +7,7 @@
 class User < ActiveRecord::Base
 
   has_and_belongs_to_many :roles
+  has_and_belongs_to_many :groups
 
   has_many :test_requests, -> {order(submitted_at: DESC)}
 
@@ -290,7 +291,11 @@
 
   def available_problems
     if not GraderConfiguration.multicontests?
-      return Problem.available_problems
+      if GraderConfiguration.use_problem_group?
+        return available_problems_in_group
+      else
+        return Problem.available_problems
+      end
     else
       contest_problems = []
       pin = {}
@@ -307,6 +312,14 @@
     end
   end
 
+  def available_problems_in_group
+    problem = []
+    self.groups.each do |group|
+      group.problems.where(available: true).each { |p| problem << p }
+    end
+    return problem.uniq
+  end
+
   def can_view_problem?(problem)
     if not GraderConfiguration.multicontests?
       return problem.available
diff --git a/app/views/contests/edit.html.erb b/app/views/contests/edit.html.erb
deleted file mode 100644
--- a/app/views/contests/edit.html.erb
+++ /dev/null
@@ -1,29 +0,0 @@
-<h1>Editing contest</h1>
-
-<%= form_for(@contest) do |f| %>
-  <%= f.error_messages %>
-
-  <table>
-    <tr>
-      <td><%= f.label :name %></td>
-      <td><%= f.text_field :name %></td>
-    </tr>
-    <tr>
-      <td><%= f.label :title %></td>
-      <td><%= f.text_field :title %></td>
-    </tr>
-    <tr>
-      <td></td>
-      <td>
-	<%= f.check_box :enabled %>
-	<%= f.label :enabled %>
-      </td>
-    </tr>
-  </table>
-  <p>
-    <%= f.submit 'Update' %>
-  </p>
-<% end %>
-
-<%= link_to 'Show', @contest %> |
-<%= link_to 'Back', contests_path %>
diff --git a/app/views/contests/edit.html.haml b/app/views/contests/edit.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/contests/edit.html.haml
@@ -0,0 +1,20 @@
+%h1 Editing contest
+= form_for(@contest) do |f|
+  = f.error_messages
+  %table
+    %tr
+      %td= f.label :name
+      %td= f.text_field :name
+    %tr
+      %td= f.label :title
+      %td= f.text_field :title
+    %tr
+      %td
+      %td
+        = f.check_box :enabled
+        = f.label :enabled
+  %p
+    = f.submit 'Update'
+= link_to 'Show', @contest
+|
+= link_to 'Back', contests_path
diff --git a/app/views/contests/index.html.erb b/app/views/contests/index.html.erb
deleted file mode 100644
--- a/app/views/contests/index.html.erb
+++ /dev/null
@@ -1,29 +0,0 @@
-<h1>Listing contests</h1>
-
-<div class="infobox">
-  <b>Go back to:</b> [<%= link_to 'contest management', :controller => 'contest_management', :action => 'index' %>]
-</div>
-
-<table>
-  <tr>
-    <th>Name</th>
-    <th>Title</th>
-    <th>Enabled</th> 
-  </tr>
-
-<% @contests.each do |contest| %>
-  <% @contest = contest %>
-  <tr>
-    <td><%= in_place_editor_field :contest, :name, {}, :rows => 1 %></td>
-    <td><%= in_place_editor_field :contest, :title, {}, :rows => 1 %></td>
-    <td><%= in_place_editor_field :contest, :enabled, {}, :rows => 1 %></td>
-    <td><%= link_to 'Show', contest %></td>
-    <td><%= link_to 'Edit', edit_contest_path(contest) %></td>
-    <td><%= link_to 'Destroy', contest, :confirm => 'Are you sure?', :method => :delete %></td>
-  </tr>
-<% end %>
-</table>
-
-<br />
-
-<%= link_to 'New contest', new_contest_path %>
diff --git a/app/views/contests/index.html.haml b/app/views/contests/index.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/contests/index.html.haml
@@ -0,0 +1,27 @@
+%h1 Listing contests
+.infobox
+  %b Go back to:
+  [#{link_to 'contest management', :controller => 'contest_management', :action => 'index'}]
+%p= link_to 'New contest', new_contest_path, class: 'btn btn-success'
+%table.table.table-striped
+  %tr
+    %th Name
+    %th Title
+    %th Enabled
+    %th
+    %th
+    %th
+
+  - @contests.each do |contest|
+    - @contest = contest
+    %tr
+      -#%td= in_place_editor_field :contest, :name, {}, :rows => 1
+      -#%td= in_place_editor_field :contest, :title, {}, :rows => 1
+      -#%td= in_place_editor_field :contest, :enabled, {}, :rows => 1
+      %td= best_in_place @contest, :name
+      %td= best_in_place @contest, :title
+      %td= best_in_place @contest, :enabled
+      %td= link_to 'Show', contest
+      %td= link_to 'Edit', edit_contest_path(contest)
+      %td= link_to 'Destroy', contest, :confirm => 'Are you sure?', :method => :delete
+%br/
diff --git a/app/views/contests/new.html.erb b/app/views/contests/new.html.erb
deleted file mode 100644
--- a/app/views/contests/new.html.erb
+++ /dev/null
@@ -1,23 +0,0 @@
-<h1>New contest</h1>
-
-<%= form_for(@contest) do |f| %>
-  <%= f.error_messages %>
-
-  <p>
-    <%= f.label :name %><br />
-    <%= f.text_field :name %>
-  </p>
-  <p>
-    <%= f.label :title %><br />
-    <%= f.text_field :title %>
-  </p>
-  <p>
-    <%= f.label :enabled %><br />
-    <%= f.check_box :enabled %>
-  </p>
-  <p>
-    <%= f.submit 'Create' %>
-  </p>
-<% end %>
-
-<%= link_to 'Back', contests_path %>
diff --git a/app/views/contests/new.html.haml b/app/views/contests/new.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/contests/new.html.haml
@@ -0,0 +1,18 @@
+%h1 New contest
+= form_for(@contest) do |f|
+  = f.error_messages
+  %p
+    = f.label :name
+    %br/
+    = f.text_field :name
+  %p
+    = f.label :title
+    %br/
+    = f.text_field :title
+  %p
+    = f.label :enabled
+    %br/
+    = f.check_box :enabled
+  %p
+    = f.submit 'Create'
+= link_to 'Back', contests_path
diff --git a/app/views/contests/show.html.erb b/app/views/contests/show.html.erb
deleted file mode 100644
--- a/app/views/contests/show.html.erb
+++ /dev/null
@@ -1,14 +0,0 @@
-<h1>Contest: <%=h @contest.title %></h1>
-
-<div class="infobox">
-  <b>Go back to:</b> [<%= link_to 'contest management', :controller => 'contest_management', :action => 'index' %>]
-</div>
-
-<p>
-  <b>Enabled:</b>
-  <%=h @contest.enabled %>
-</p>
-
-
-<%= link_to 'Edit', edit_contest_path(@contest) %> |
-<%= link_to 'Back', contests_path %>
diff --git a/app/views/contests/show.html.haml b/app/views/contests/show.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/contests/show.html.haml
@@ -0,0 +1,11 @@
+%h1
+  Contest: #{h @contest.title}
+.infobox
+  %b Go back to:
+  [#{link_to 'contest management', :controller => 'contest_management', :action => 'index'}]
+%p
+  %b Enabled:
+  = h @contest.enabled
+= link_to 'Edit', edit_contest_path(@contest)
+|
+= link_to 'Back', contests_path
diff --git a/app/views/groups/_form.html.haml b/app/views/groups/_form.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/_form.html.haml
@@ -0,0 +1,16 @@
+= form_for @group do |f|
+  - if @group.errors.any?
+    #error_explanation
+      %h2= "#{pluralize(@group.errors.count, "error")} prohibited this group from being saved:"
+      %ul
+        - @group.errors.full_messages.each do |msg|
+          %li= msg
+
+  .form-group.field
+    = f.label :name
+    = f.text_field :name, class: 'form-control'
+  .form-group.field
+    = f.label :description
+    = f.text_field :description, class: 'form-control'
+  .form-group.actions
+    = f.submit 'Save', class: 'btn btn-primary'
diff --git a/app/views/groups/edit.html.haml b/app/views/groups/edit.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/edit.html.haml
@@ -0,0 +1,7 @@
+%h1 Editing group
+
+= render 'form'
+
+= link_to 'Show', @group
+\|
+= link_to 'Back', groups_path
diff --git a/app/views/groups/index.html.haml b/app/views/groups/index.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/index.html.haml
@@ -0,0 +1,22 @@
+%h1 Groups
+
+%p
+  = link_to 'New Group', new_group_path, class: 'btn btn-primary'
+%table.table.table-hover
+  %thead
+    %tr
+      %th Name
+      %th Description
+      %th
+      %th
+
+  %tbody
+    - @groups.each do |group|
+      %tr
+        %td= group.name
+        %td= group.description
+        %td= link_to 'View', group, class: 'btn btn-default'
+        %td= link_to 'Destroy', group, :method => :delete, :data => { :confirm => 'Are you sure?' }, class: 'btn btn-danger'
+
+%br
+
diff --git a/app/views/groups/new.html.haml b/app/views/groups/new.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/new.html.haml
@@ -0,0 +1,5 @@
+%h1 New group
+
+= render 'form'
+
+= link_to 'Back', groups_path
diff --git a/app/views/groups/show.html.haml b/app/views/groups/show.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/groups/show.html.haml
@@ -0,0 +1,72 @@
+%p
+  %b Name:
+  = @group.name
+%p
+  %b Description:
+  = @group.description
+
+%br
+= link_to 'Edit', edit_group_path(@group)
+\|
+= link_to 'Back', groups_path
+
+.row
+  %h1 Group details
+.row
+  .col-md-6
+    .panel.panel-default
+      .panel-heading
+        .panel-title Users in this group
+      .panel-body
+        =form_tag add_user_group_path(@group), class: 'form-inline' do
+          .form-group
+            =label_tag :user_id, "User"
+            =select_tag :user_id, options_from_collection_for_select(User.all,'id','full_name'), class: 'select2'
+          =submit_tag "Add",class: 'btn btn-primary'
+
+
+        %table.table.table-hover
+          %thead
+            %tr
+              %th Login
+              %th Full name
+              %th Remark
+              %th
+
+          %tbody
+            - @group.users.each do |user|
+              %tr
+                %td= user.login
+                %td= user.full_name
+                %td= user.remark
+                %td= link_to 'Remove', remove_user_group_path(@group,user), :method => :delete, :data => { :confirm => "Remove #{user.full_name}?" }, class: 'btn btn-danger'
+  .col-md-6
+    .panel.panel-default
+      .panel-heading
+        .panel-title Problems
+      .panel-body
+
+        =form_tag add_problem_group_path(@group), class: 'form-inline' do
+          .form-group
+            =label_tag :problem_id, "Problem"
+            =select_tag :problem_id, options_from_collection_for_select(Problem.all,'id','full_name'), class: 'select2'
+          =submit_tag "Add",class: 'btn btn-primary'
+
+
+        %table.table.table-hover
+          %thead
+            %tr
+              %th name
+              %th Full name
+              %th Full score
+              %th
+
+          %tbody
+            - @group.problems.each do |problem|
+              %tr
+                %td= problem.name
+                %td= problem.full_name
+                %td= problem.full_score
+                %td= link_to 'Remove', remove_problem_group_path(@group,problem), :method => :delete, :data => { :confirm => "Remove #{problem.full_name}?" }, class: 'btn btn-danger'
+
+
diff --git a/app/views/layouts/_header.html.haml b/app/views/layouts/_header.html.haml
--- a/app/views/layouts/_header.html.haml
+++ b/app/views/layouts/_header.html.haml
@@ -47,6 +47,7 @@
                 = add_menu( 'Announcements', 'announcements', 'index')
                 = add_menu( 'Problems', 'problems', 'index')
                 = add_menu( 'Users', 'user_admin', 'index')
+                = add_menu( 'User Groups', 'groups', 'index')
                 = add_menu( 'Graders', 'graders', 'list')
                 = add_menu( 'Message ', 'messages', 'console')
                 %li.divider{role: 'separator'}
diff --git a/app/views/problems/manage.html.haml b/app/views/problems/manage.html.haml
--- a/app/views/problems/manage.html.haml
+++ b/app/views/problems/manage.html.haml
@@ -39,7 +39,7 @@
 %p= link_to '[Back to problem list]', :action => 'list'
 
 = form_tag :action=>'do_manage' do
-  .submitbox
+  .submitbox.panel
     What do you want to do to the selected problem?
     %br/
     (You can shift-click to select a range of problems)
@@ -59,8 +59,13 @@
           Add to 
           = select("contest","id",Contest.all.collect {|c| [c.title, c.id]})
           = submit_tag 'Add', :name => 'add_to_contest'
+      %li
+        Add problems to group
+        = select_tag "group_id", options_from_collection_for_select( Group.all, 'id','name',params[:group_name]), id: 'group_name',class: 'select2'
+        = submit_tag 'Add', name: 'add_group'
+          
 
-  %table
+  %table.table.table-hover
     %tr{style: "text-align: left;"}
       %th= check_box_tag 'select_all'
       %th Name
diff --git a/app/views/user_admin/_form.html.erb b/app/views/user_admin/_form.html.erb
deleted file mode 100644
--- a/app/views/user_admin/_form.html.erb
+++ /dev/null
@@ -1,25 +0,0 @@
-<%= error_messages_for 'user' %>
-
-<!--[form:user]-->
-<p><label for="user_name">Login</label><br/>
-<%= text_field 'user', 'login'  %></p>
-
-<p><label for="user_name">Full name</label><br/>
-<%= text_field 'user', 'full_name'  %></p>
-
-<p><label for="password">Password</label><br/>
-<%= password_field 'user', 'password'  %></p>
-
-<p><label for="password_confirmation">Password (confirm)</label><br/>
-<%= password_field 'user', 'password_confirmation'  %></p>
-
-<p><label for="user_email">E-mail</label><br/>
-<%= email_field 'user', 'email'  %></p>
-
-<p><label for="user_alias">Alias</label><br/>
-<%= text_field 'user', 'alias'  %></p>
-
-<p><label for="user_remark">Remark</label><br/>
-<%= text_field 'user', 'remark'  %></p>
-<!--[eoform:user]-->
-
diff --git a/app/views/user_admin/_form.html.haml b/app/views/user_admin/_form.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/user_admin/_form.html.haml
@@ -0,0 +1,31 @@
+= error_messages_for 'user'
+/ [form:user]
+.form-group
+  %label.col-md-2.control-label{for: :login} Login
+  .col-md-4
+    = text_field 'user', 'login', class: 'form-control'
+.form-group
+  %label.col-md-2.control-label{for: :full_name} Full name
+  .col-md-4
+    = text_field 'user', 'full_name', class: 'form-control'
+.form-group
+  %label.col-md-2.control-label{for: :password} Password
+  .col-md-4
+    = password_field 'user', 'password', class: 'form-control'
+.form-group
+  %label.col-md-2.control-label{for: :password_confirmation} Password (confirm)
+  .col-md-4
+    = password_field 'user', 'password_confirmation', class: 'form-control'
+.form-group
+  %label.col-md-2.control-label{for: :email} E-mail
+  .col-md-4
+    = email_field 'user', 'email', class: 'form-control'
+.form-group
+  %label.col-md-2.control-label{for: :alias} Alias
+  .col-md-4
+    = text_field 'user', 'alias', class: 'form-control'
+.form-group
+  %label.col-md-2.control-label{for: :remark} Remark
+  .col-md-4
+    = text_field 'user', 'remark', class: 'form-control'
+/ [eoform:user]
diff --git a/app/views/user_admin/bulk_manage.html.haml b/app/views/user_admin/bulk_manage.html.haml
--- a/app/views/user_admin/bulk_manage.html.haml
+++ b/app/views/user_admin/bulk_manage.html.haml
@@ -46,6 +46,15 @@
             %label.checkbox-inline
               = check_box_tag "gen_password", true, params[:gen_password]
               Generate new random password
+        .row.form-group
+          .col-md-4
+            %label.checkbox-inline
+              = check_box_tag "add_group", true, params[:add_group]
+              Add users to group
+          %label.col-md-3.control-label.text-right Group name
+          .col-md-5
+            = select_tag "group_name", options_from_collection_for_select( Group.all, 'id','name',params[:group_name]), id: 'group_name',class: 'form-control select2'
+
 
 .row
   .col-md-12
diff --git a/app/views/user_admin/edit.html.haml b/app/views/user_admin/edit.html.haml
--- a/app/views/user_admin/edit.html.haml
+++ b/app/views/user_admin/edit.html.haml
@@ -1,9 +1,11 @@
 %h1 Editing user
 
-= form_tag :action => 'update', :id => @user do
+= form_tag( {:action => 'update', :id => @user}, {class: 'form-horizontal'}) do
   = error_messages_for 'user'
   = render partial: "form"
-  = submit_tag "Edit"
+  .form-group
+    .col-md-offset-2.col-md-4
+      = submit_tag "Edit", class: 'btn btn-primary'
 
 
 = link_to 'Show', :action => 'show', :id => @user 
diff --git a/app/views/user_admin/show.html.erb b/app/views/user_admin/show.html.erb
deleted file mode 100644
--- a/app/views/user_admin/show.html.erb
+++ /dev/null
@@ -1,10 +0,0 @@
-<h1>User information</h1>
-
-<% for column in User.content_columns %>
-<p>
-  <b><%= column.human_name %>:</b> <%=h @user.send(column.name) %>
-</p>
-<% end %>
-
-<%= link_to 'Edit', :action => 'edit', :id => @user %> |
-<%= link_to 'Back', :action => 'list' %>
diff --git a/app/views/user_admin/show.html.haml b/app/views/user_admin/show.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/user_admin/show.html.haml
@@ -0,0 +1,14 @@
+%h1 User information
+- for column in User.content_columns
+  %p
+    %b
+      = column.human_name
+      \:
+    = h @user.send(column.name)
+%p
+  %strong Group
+  \:
+  = @user.groups.map{ |x| link_to(x.name,group_path(x)).html_safe}.join(', ').html_safe
+= link_to 'Edit', :action => 'edit', :id => @user
+|
+= link_to 'Back', :action => 'index'
diff --git a/config/routes.rb b/config/routes.rb
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -29,7 +29,15 @@
       get 'import'
       get 'manage'
     end
+  end
 
+  resources :groups do
+    member do
+      post 'add_user', to: 'groups#add_user', as: 'add_user'
+      delete 'remove_user/:user_id', to: 'groups#remove_user', as: 'remove_user'
+      post 'add_problem', to: 'groups#add_problem', as: 'add_problem'
+      delete 'remove_problem/:problem_id', to: 'groups#remove_problem', as: 'remove_problem'
+    end
   end
 
   resources :testcases, only: [] do
diff --git a/db/migrate/011_add_language_ext.rb b/db/migrate/011_add_language_ext.rb
--- a/db/migrate/011_add_language_ext.rb
+++ b/db/migrate/011_add_language_ext.rb
@@ -3,7 +3,7 @@
     add_column :languages, :ext, :string, :limit => 10
 
     Language.reset_column_information
-    langs = Language.find(:all)
+    langs = Language.all
     langs.each do |l|
       l.ext = l.name
       l.save
diff --git a/db/migrate/015_add_status_to_tasks.rb b/db/migrate/015_add_status_to_tasks.rb
--- a/db/migrate/015_add_status_to_tasks.rb
+++ b/db/migrate/015_add_status_to_tasks.rb
@@ -4,7 +4,7 @@
     add_column :tasks, :updated_at, :datetime
 
     Task.reset_column_information
-    Task.find(:all).each do |task|
+    Task.all.each do |task|
       task.status_complete
       task.save
     end
diff --git a/db/migrate/018_add_number_to_submissions.rb b/db/migrate/018_add_number_to_submissions.rb
--- a/db/migrate/018_add_number_to_submissions.rb
+++ b/db/migrate/018_add_number_to_submissions.rb
@@ -9,8 +9,7 @@
     last_problem_id = nil
     current_number = 0
 
-    Submission.find(:all, 
-                    :order => 'user_id, problem_id, submitted_at').each do |submission|
+    Submission.order('user_id, problem_id, submitted_at').each do |submission|
       if submission.user_id==last_user_id and submission.problem_id==last_problem_id
         current_number += 1
       else
diff --git a/db/migrate/025_add_site_to_user_and_add_default_site.rb b/db/migrate/025_add_site_to_user_and_add_default_site.rb
--- a/db/migrate/025_add_site_to_user_and_add_default_site.rb
+++ b/db/migrate/025_add_site_to_user_and_add_default_site.rb
@@ -7,7 +7,7 @@
     add_column :users, :site_id, :integer
     User.reset_column_information
 
-    User.find(:all).each do |user|
+    User.all.each do |user|
 
       class << user
         def valid?
diff --git a/db/migrate/028_refactor_problem_body_to_description.rb b/db/migrate/028_refactor_problem_body_to_description.rb
--- a/db/migrate/028_refactor_problem_body_to_description.rb
+++ b/db/migrate/028_refactor_problem_body_to_description.rb
@@ -3,7 +3,7 @@
     add_column :problems, :description_id, :integer
     Problem.reset_column_information
     
-    Problem.find(:all).each do |problem|
+    Problem.all.each do |problem|
       if problem.body!=nil
         description = Description.new
         description.body = problem.body
@@ -21,7 +21,7 @@
     add_column :problems, :body, :text
     Problem.reset_column_information
 
-    Problem.find(:all).each do |problem|
+    Problem.all.each do |problem|
       if problem.description_id != nil
         problem.body = Description.find(problem.description_id).body
         problem.save
diff --git a/db/migrate/029_add_test_allowed_to_problems.rb b/db/migrate/029_add_test_allowed_to_problems.rb
--- a/db/migrate/029_add_test_allowed_to_problems.rb
+++ b/db/migrate/029_add_test_allowed_to_problems.rb
@@ -3,7 +3,7 @@
     add_column :problems, :test_allowed, :boolean
     Problem.reset_column_information
 
-    Problem.find(:all).each do |problem|
+    Problem.all.each do |problem|
       problem.test_allowed = true
       problem.save
     end
diff --git a/db/migrate/20081204122651_add_activated_to_users.rb b/db/migrate/20081204122651_add_activated_to_users.rb
--- a/db/migrate/20081204122651_add_activated_to_users.rb
+++ b/db/migrate/20081204122651_add_activated_to_users.rb
@@ -4,7 +4,7 @@
 
     User.reset_column_information
 
-    User.find(:all).each do |user|
+    User.all.each do |user|
 
       # disable validation
       class <<user
diff --git a/db/migrate/20090416235658_add_common_ext_to_languages.rb b/db/migrate/20090416235658_add_common_ext_to_languages.rb
--- a/db/migrate/20090416235658_add_common_ext_to_languages.rb
+++ b/db/migrate/20090416235658_add_common_ext_to_languages.rb
@@ -11,7 +11,7 @@
       'cpp' => 'cpp,cc',
       'pas' => 'pas' 
     }
-    Language.find(:all).each do |lang|
+    Language.all.each do |lang|
       lang.common_ext = common_ext[lang.name]
       lang.save
     end
diff --git a/db/migrate/20170911091143_create_groups.rb b/db/migrate/20170911091143_create_groups.rb
new file mode 100644
--- /dev/null
+++ b/db/migrate/20170911091143_create_groups.rb
@@ -0,0 +1,30 @@
+class CreateGroups < ActiveRecord::Migration
+
+  def change
+    create_table :groups do |t|
+      t.string :name
+      t.string :description
+    end
+
+    create_join_table :groups, :users do |t|
+      # t.index [:group_id, :user_id]
+      t.index [:user_id, :group_id]
+    end
+
+    create_join_table :problems, :groups do |t|
+      # t.index [:problem_id, :group_id]
+      t.index [:group_id, :problem_id]
+    end
+
+    reversible do |change|
+      change.up do
+        GraderConfiguration.where(key: 'system.use_problem_group').first_or_create(value_type: 'boolean', value: 'false',
+                                                                                   description: 'If true, available problem to the user will be only ones associated with the group of the user');
+      end
+
+      change.down do
+        GraderConfiguration.where(key: 'system.use_problem_group').destroy_all
+      end
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170427070345) do
+ActiveRecord::Schema.define(version: 20170911091143) do
 
   create_table "announcements", force: :cascade do |t|
     t.string   "author",       limit: 255
@@ -79,6 +79,25 @@
 
   add_index "grader_processes", ["host", "pid"], name: "index_grader_processes_on_ip_and_pid", using: :btree
 
+  create_table "groups", force: :cascade do |t|
+    t.string "name",        limit: 255
+    t.string "description", limit: 255
+  end
+
+  create_table "groups_problems", id: false, force: :cascade do |t|
+    t.integer "problem_id", limit: 4, null: false
+    t.integer "group_id",   limit: 4, null: false
+  end
+
+  add_index "groups_problems", ["group_id", "problem_id"], name: "index_groups_problems_on_group_id_and_problem_id", using: :btree
+
+  create_table "groups_users", id: false, force: :cascade do |t|
+    t.integer "group_id", limit: 4, null: false
+    t.integer "user_id",  limit: 4, null: false
+  end
+
+  add_index "groups_users", ["user_id", "group_id"], name: "index_groups_users_on_user_id_and_group_id", using: :btree
+
   create_table "heart_beats", force: :cascade do |t|
     t.integer  "user_id",    limit: 4
     t.string   "ip_address", limit: 255
diff --git a/db/seeds.rb b/db/seeds.rb
--- a/db/seeds.rb
+++ b/db/seeds.rb
@@ -163,7 +163,16 @@
      :value_type => 'string',
      :default_value => 'none',
      :description => "New user will be assigned to this contest automatically, if it exists.  Set to 'none' if there is no default contest."
-   }
+   },
+
+   {
+     :key => 'system.use_problem_group',
+     :value_type => 'boolean',
+     :default_value => 'false',
+     :description => "If true, available problem to the user will be only ones associated with the group of the user."
+   },
+
+
 
   ]
 
diff --git a/test/controllers/groups_controller_test.rb b/test/controllers/groups_controller_test.rb
new file mode 100644
--- /dev/null
+++ b/test/controllers/groups_controller_test.rb
@@ -0,0 +1,49 @@
+require 'test_helper'
+
+class GroupsControllerTest < ActionController::TestCase
+  setup do
+    @group = groups(:one)
+  end
+
+  test "should get index" do
+    get :index
+    assert_response :success
+    assert_not_nil assigns(:groups)
+  end
+
+  test "should get new" do
+    get :new
+    assert_response :success
+  end
+
+  test "should create group" do
+    assert_difference('Group.count') do
+      post :create, group: { description: @group.description, name: @group.name }
+    end
+
+    assert_redirected_to group_path(assigns(:group))
+  end
+
+  test "should show group" do
+    get :show, id: @group
+    assert_response :success
+  end
+
+  test "should get edit" do
+    get :edit, id: @group
+    assert_response :success
+  end
+
+  test "should update group" do
+    patch :update, id: @group, group: { description: @group.description, name: @group.name }
+    assert_redirected_to group_path(assigns(:group))
+  end
+
+  test "should destroy group" do
+    assert_difference('Group.count', -1) do
+      delete :destroy, id: @group
+    end
+
+    assert_redirected_to groups_path
+  end
+end