C++ Program to Solve Travelling Salesman Problem for Unweighted Graph

Anvi Jain

Answered on 18th Jun, 2019

Travelling Salesman Problem use to calculate the shortest route to cover all the cities and return back to the origin city. This method is use to find the shortest path to cover all the nodes of a graph.

This is the program to find shortest route of a unweighted graph.

Algorithm

Begin
   Define a variable vr = 4 universally.
   Declare an integer function TSP to implement Travelling salesman Problem.
   Declare a graph grph[][] as a 2D matrix and variable p to the integer datatype.
   Pass them as a parameter.
   Declare variable ver to the vector datatype.
   for (int i = 0; i < vr; i++)
      if (i != p) then
         Call push_back(i) function to store the value of all vertex except source vertex.
         Initialize m_p = INT_MAX to store minimum weight of a graph.
      do
         Declare cur_pth, k to the integer datatype.
            initialize cur_pth = 0.
            initialize k = p.
         for (int i = 0; i < ver.size(); i++)
            cur_pth += grph[k][ver[i]].
            k = ver[i].
         cur_pth += grph[k][p].
         m_p = min(m_p, cur_pth) to update the value of minimum weight.
         while (next_permutation(ver.begin(), ver.end())).
         Return m_p.
   Declare a graph grph[][] as a 2D matrix to the integer datatype.
      Initialize values of grph[][] graph.
   Declare variable p to the integer datatype.
      Initialize p = 0.
   Print “The result is: ”.
   Print the return value of TSP() function.
End.

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
#define vr 4
int TSP(int grph[][vr], int p) // implement traveling Salesman Problem. {
   vector<int> ver; //
   for (int i = 0; i < vr; i++)
      if (i != p)
         ver.push_back(i);
         int m_p = INT_MAX; // store minimum weight of a graph
   do {
      int cur_pth = 0;
      int k = p;
      for (int i = 0; i < ver.size(); i++) {
         cur_pth += grph[k][ver[i]];
         k = ver[i];
      }
      cur_pth += grph[k][p];
      m_p = min(m_p, cur_pth); // to update the value of minimum weight
   }
   while (next_permutation(ver.begin(), ver.end()));
   return m_p;
}
int main() {
   int grph[][vr] = { { 0, 5, 10, 15 }, //values of a graph in a form of matrix
      { 5, 0, 20, 30 },
      { 10, 20, 0, 35 },
      { 15, 30, 35, 0 }
   };
   int p = 0;
   cout<< "\n The result is: "<< TSP(grph, p) << endl;
   return 0;
}

Output

The result is: 75