C++ Program to Implement Johnson’s Algorithm

This is a C++ Program to implement Johnson’s Algorithm. Johnson’s algorithm helps to find shortest path between given source and destination nodes.

Here is source code of the C++ Program to Implement Johnson’s Algorithm. The C++ program is successfully compiled and run on a Linux system. The program output is also shown below.

  1. #include<iostream>
  2. #include<conio.h>
  3.  
  4. using namespace std;
  5.  
  6. int min(int a, int b);
  7. int cost[10][10], a[10][10], i, j, k, c;
  8.  
  9. int min(int a, int b)
  10. {
  11.     if (a < b)
  12.         return a;
  13.     else
  14.         return b;
  15. }
  16.  
  17. int main(int argc, char **argv)
  18. {
  19.     int n, m;
  20.     cout << "Enter no of vertices";
  21.     cin >> n;
  22.     cout << "Enter no of edges";
  23.     cin >> m;
  24.     cout << "Enter the\nEDGE Cost\n";
  25.     for (k = 1; k <= m; k++)
  26.     {
  27.         cin >> i >> j >> c;
  28.         a[i][j] = cost[i][j] = c;
  29.     }
  30.     for (i = 1; i <= n; i++)
  31.         for (j = 1; j <= n; j++)
  32.         {
  33.             if (a[i][j] == 0 && i != j)
  34.                 a[i][j] = 31999;
  35.         }
  36.     for (k = 1; k <= n; k++)
  37.         for (i = 1; i <= n; i++)
  38.             for (j = 1; j <= n; j++)
  39.                 a[i][j] = min(a[i][j], a[i][k] + a[k][j]);
  40.     cout << "Resultant adj matrix\n";
  41.     for (i = 1; i <= n; i++)
  42.     {
  43.         for (j = 1; j <= n; j++)
  44.         {
  45.             if (a[i][j] != 31999)
  46.                 cout << a[i][j] << " ";
  47.         }
  48.         cout << "\n";
  49.     }
  50.     return 0;
  51. }

Output:

$ g++ JohnsonsShortestPath.cpp
$ a.out
 
Enter no of vertices 3
Enter no of edges 5
Enter the
EDGE Cost
1 2 4
2 1 6
1 3 11
3 1 3
2 3 2
Resultant adj matrix
0 4 6 
5 0 2 
3 7 0 
 
------------------
(program exited with code: 0)
Press return to continue

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