moduinverse.c

#include<stdio.h>
#define N 3
int modinverse(int a,int b)
{
    int z=a;
    int q,r,t1=0,t2=1,t;
    while(b<0){
        b=b+a;
    }
    while(a>1)
    {
      r=a%b;
      q=a/b;
      a=b;
      b=r;
      t=t1-q*t2;
      t1=t2;
      t2=t;
    }
    if(t1<0)
        t1+=z;
        return t1;
}
int determinant(int mat[N][N],int n)
{
    int d=0,f;
    if(n==1)
        return mat[0][0];
    int temp[n][n];
    int sign=1;
    for(f=0;f<n;f++)
    {
        getcofactor(mat,temp,0,f,n);
        d+=sign*mat[0][f]*determinant(temp,n-1);
        sign=-sign;
    }
    return d;
}
void getcofactor(int mat[N][N],int temp[N][N],int p,int q,int n)
{
        int i=0,j=0,row,col;
        for(row=0;row<n;row++)
        {
            for(col=0;col<n;col++)
            {
                if(row!=p && col!=q)
                {
                    temp[i][j++]=mat[row][col];
                    if(j==n-1)
                    {
                       j=0;
                       i++;
                    }
                }
            }
        }
}
void adjoint(int A[N][N],int adj[N][N])
{
    if (N == 1)
    {
        adj[0][0] = 1;
        return;
    }
    int sign = 1, temp[N][N];

    for (int i=0; i<N; i++)
    {
        for (int j=0; j<N; j++)
        {
            getcofactor(A, temp, i, j, N);

            sign = ((i+j)%2==0)? 1: -1;

            adj[j][i] = (sign)*(determinant(temp, N-1));
        }
    }
}
void display(int mat[N][N],int n)
{
    int i,j;
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
            {
            printf("%d ",mat[i][j]);
            }
    printf("\n");
    }
}
void solution(int A[N][N],int C[N],int mi,int mo)
{
    int i,j,D[N];
   for(i=0;i<N;i++)
    {
        for(j=0;j<N;j++)
        {
            D[i]=D[i]+(A[i][j]*C[j]);
        }
    }
    for(i=0;i<N;i++)
        printf("%d  ",D[i]);

}
int main()
{
    int i,j,n,mat[N][N],det,C[N];
    int adj[N][N],mod,mdinverse,D[N];
    printf("enter the mod value\n");
    scanf("%d",&mod);
    printf("enter the size of matrix\n");
    scanf("%d",&n);
    printf("enter the elemants of array\n");
    for(i=0;i<n;i++)
    {
        for(j=0;j<n;j++)
        {
            scanf("%d",&mat[i][j]);
        }
    }
    printf("enter the elemants of coefficent matrix\n");
    for(i=0;i<n;i++)
    {
        scanf("%d",&C[i]);
    }
    det=determinant(mat,n);
    printf("Determinant of the matrix is : %d\n",det);
    mdinverse=modinverse(mod,det);
    printf("modular inverse is : %d\n",mdinverse);
    adjoint(mat,adj);
    display(adj,n);
    solution(adj,C,mdinverse,mod);
    //for(i=0;i<n;i++)
    //{
      //  printf("%d\n",D[i]);
   // }
   return 0;
}