C Program for Matrix Multiplication

This is a c program for Matrix Multiplication. To understand how it works, you should first know how matrix multiplication is done mathematically.

#include <stdio.h>
void main()
{
int m1[10][10],i,j,k,m2[10][10],prod[10][10],r1,c1,r2,c2;
printf("Enter number of rows and columns of first matrix:\n");
scanf("%d%d",&r1,&c1);
printf("Enter number of rows and columns of second matrix:\n");
scanf("%d%d",&r2,&c2);
if(r2==c1)
    {
    printf("Enter elements of First matrix (row wise):\n");
    for(i=0;i<r1;i++)
        for(j=0;j<c1;j++)
            scanf("%d",&m1[i][j]);
    printf("Matrix1 is :\n");
    for(i=0;i<r1;i++)
        {
        for(j=0;j<c1;j++)
            printf("%d ",m1[i][j]);
        printf("\n");
        }
    printf("Enter elements of Second matrix (row wise):\n");
    for(i=0;i<r2;i++)
        for(j=0;j<c2;j++)
            scanf("%d",&m2[i][j]);
    printf("Matrix2 is:\n");
    for(i=0;i<r2;i++)
        {
        for(j=0;j<c2;j++)
            printf("%d ",m2[i][j]);
        printf("\n");
        }
    printf("Product of the Matrices (M1 x M2):\n");
    for(i=0;i<r1;i++)
        {
        for(j=0;j<c2;j++)
            {
            prod[i][j]=0;
            for(k=0;k<r1;k++)
                prod[i][j]+=m1[i][k]*m2[k][j];
            printf("%d\ ",prod[i][j]);
            }
        printf("\n");
        }
    }
else
    {
    printf("Matrices can't be multiplied.\n");
    printf("No. of columns of first matrix and no of rows of second are different.");
    }
}

C Program To Represent Directed or Undirected Graph Using Adjacency Matrix

C program to represent directed or undirected graph using Adjacency matrix.

#include<stdio.h>
#include<conio.h>
#define max 20
int adj[max][max]; //Adjacency matrix
int n;  //Denotes number of nodes in the graph
void main()
 {

  int max_edges,i,j,origin,destin;
  char graph_type;
  printf("Enter number of nodes : ");
  scanf("%d",&n);
  printf("Enter type of graph, directed or undirected.\n");
   printf("Enter d for directed and u for undirected:\n ");
  fflush(stdin);
   scanf("%c",&graph_type);
   if(graph_type=='u')
    max_edges=n*(n-1)/2;
  else
    max_edges=n*(n-1);
  for(i=1;i<=max_edges;i++)
    {
    printf("Enter edge %d( 0 0 to quit ) : ",i);
    scanf("%d %d",&origin,&destin);
    if( (origin==0) && (destin==0) )
     break;
    if( origin > n || destin > n || origin<=0 || destin<=0)
     {
     printf("Invalid edge!\n");
     i--;
     }
    else
     {
     adj[origin][destin]=1;
     if( graph_type=='u')
      adj[destin][origin]=1;
     }
    }

  printf("The adjacency matrix is :\n");
  for(i=1;i<=n;i++)
    {
    for(j=1;j<=n;j++)
     printf("%4d",adj[i][j]);
    printf("\n");
    }
   getch();
  }