Graph: Program to Implement Floyd Algorithm

/* FLYOD.C */

  # include

  # define Infinity 9999
  # define size 20

  int i,k,j;
  void Input(int , int a[size][size]);
  void Output(int , int a[size][size]);
  void Flyod(int , int a[size][size], int r[size][size]);

/* Input function */

  void Input(int n, int a[size][size])
     {
int i, j;
      printf("\n Input adjacency matrix\n");
       for (i = 0; i < n; i++)
 {
   for (j = 0; j < n; j++)
    {
 scanf("%d", &a[i][j]);
    }
  printf("\n");
       }
    }

/* Output function */

 void Output (int n, int a[size][size])
     {
int i, j;
      for (i =0; i < n; i++)
 {
   for (j =0; j < n; j++)
    {
      printf(" %d", a[i][j]);
    }
  printf("\n");
       }
    }

/* Shortest path evaluation function */

  void Flyod(int n, int a[size][size], int r[size][size])
       {
  for (i = 0; i < n; i ++)
    a[i][i] = 0;  /* Set diagonal elements zero */
    printf("\n After setting diagonal elements to zero \n");
    Output(n, a);
    for (i = 0; i < n; i++)
      {
       for (j = 0; j < n; j++)
        {
  if ((a[i][j] == 0) && (i != j))
   r[i][j] = Infinity;
   else
    r[i][j] = a[i][j];
        }
     }
     printf("\n Replacing zeros by very large value \n");
     Output(n, r);
   for (k = 0; k < n; k++)
   {
    for (i = 0; i < n; i++)
      {
       for (j = 0; j < n; j++)
        {
    if (r[i][k] + r[k][j]< r[i][j])
       {
        printf("\n r[%d][%d] = %d ", i, k, r[i][k]);
        printf("\n r[%d][%d] = %d ", k, j, r[k][j]);
        printf("\n r[%d][%d] = %d ", i, j, r[i][j]);
        r[i][j] = r[i][k] +  r[k][j];
        printf("\n r[%d][%d] = r[%d][%d] + r[%d][%d] = %d ", i, j, i, k, k, j, r[i][j]);
       }
       else
       {
         r[i][j] = r[i][j];
        printf("\n r[%d][%d] = r[%d][%d] = %d ", i, j, i, j, r[i][j]);
       }
       }
       printf("\n");
     }
     printf("\n Step %d \n", k);
     Output (n,r);
 }
      }

/* Function main */

    void main()
       {
  int a[size][size];
  int r[size][size];
  int n;
  printf("\n Input number of vertices in the graph: ");
  scanf("%d", &n);
  Input(n,a);
  printf("\n Adjacency matrix\n");
 Output(n,a);
 Flyod(n,a,r);
 printf("\n Shortest path matrix \n");
  Output(n,r);
      }