From f00c7e0f42d01924edaf6b7c6241aa4a709dc7ac Mon Sep 17 00:00:00 2001
From: Davis King <davis@dlib.net>
Date: Sun, 7 Dec 2014 12:11:13 -0500
Subject: [PATCH] Added max cost assignment example program

---
 examples/CMakeLists.txt             |  1 +
 examples/max_cost_assignment_ex.cpp | 47 +++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100755 examples/max_cost_assignment_ex.cpp

diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index a615a53f7..144792ff1 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -56,6 +56,7 @@ add_example(logger_ex)
 add_example(logger_ex_2)
 add_example(matrix_ex)
 add_example(matrix_expressions_ex)
+add_example(max_cost_assignment_ex)
 add_example(member_function_pointer_ex)
 add_example(mlp_ex)
 add_example(model_selection_ex)
diff --git a/examples/max_cost_assignment_ex.cpp b/examples/max_cost_assignment_ex.cpp
new file mode 100755
index 000000000..f6985a9e3
--- /dev/null
+++ b/examples/max_cost_assignment_ex.cpp
@@ -0,0 +1,47 @@
+// The contents of this file are in the public domain. See LICENSE_FOR_EXAMPLE_PROGRAMS.txt
+/*
+ 
+ This simple example shows how to call dlib's optimal linear assignment problem solver.
+ It is an implementation of the famous Hungarian algorithm and is quite fast, operating in
+ O(N^3) time.
+
+*/
+
+#include <dlib/optimization/max_cost_assignment.h>
+#include <iostream>
+
+using namespace std;
+using namespace dlib;
+
+int main ()
+{
+    // Let's imagine you need to assign N people to N jobs.  Additionally, each person will make
+    // your company a certain amount of money at each job, but each person has different skills
+    // so they are better at some jobs and worse at others.  You would like to find the best way
+    // to assign people to these jobs.  In particular, you would like to maximize the amount of
+    // money the group makes as a whole.  This is an example of an assignment problem and is
+    // what is solved by the max_cost_assignment() routine.
+    // 
+    // So in this example, let's imagine we have 3 people and 3 jobs.  We represent the amount of
+    // money each person will produce at each job with a cost matrix.  Each row corresponds to a
+    // person and each column corresponds to a job.  So for example, below we are saying that
+    // person 0 will make $1 at job 0, $2 at job 1, and $6 at job 2.  
+    matrix<int> cost(3,3);
+    cost = 1, 2, 6,
+           5, 3, 6,
+           4, 5, 0;
+
+    // To find out the best assignment of people to jobs we just need to call this function.
+    std::vector<long> assignment = max_cost_assignment(cost);
+
+    // This prints optimal assignments:  [2, 0, 1] which indicates that we should assign
+    // the person from the first row of the cost matrix to job 2, the middle row person to
+    // job 0, and the bottom row person to job 1.
+    for (unsigned int i = 0; i < assignment.size(); i++)
+        cout << assignment[i] << std::endl;
+
+    // This prints optimal cost:  16.0
+    // which is correct since our optimal assignment is 6+5+5.
+    cout << "optimal cost: " << assignment_cost(cost, assignment) << endl;
+}
+