C Program for Inverse of Matrix
Using Determinant And Cofactor
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#include<stdio.h>
#include<math.h>
#include<conio.h>
void trans(float
[][40], float [][40], int);
void cofac(float
[][40], int);
float
determin(float [][40], int);
int main(){
float
matrix[40][40], deter;
int a,
b, row, col,i,t;
printf("Enter the number of testcases: \n");
scanf("%d",&t);
for(i=0;i<t;i++)
{
printf("\nEnter size of the Matrix : \n");
scanf("%d %d", &row, &col);
if(row==col){
printf("\nEnter the elements of %d X %d matrix : \n", row,
col);
for(a=0;a<row;++a){
for(b=0;b<col;++b){
scanf("%f",&matrix[a][b]);
}
}
deter =
determin(matrix, row);
printf("\n The Determinant of the Matrix is : %f", deter);
if(deter == 0)
printf("\n Inverse of Matrix is not possible for the matrices
having 0 Determinant value !!\n");
else
cofac(matrix, row);
}
else
printf("\n Inverse of Matrix is
possible for Square matrix !! Kindly give same number of rows and columns
\n");
}
}
float
determin(float matrix[40][40], int k){
float
deter=0.0, z=1.0, mt[40][40];
int a,
b, c, x, y;
if(k==1)
{
return(matrix[0][0]);
}
else
{
deter=0;
for(a=0;a<k;++a){
x=0;
y=0;
for(b=0;b<k;++b){
for(c=0;c<k;++c){
mt[b][c]=0;
if((b
!= 0) && (c != a))
{
mt[x][y]=matrix[b][c];
if(y<(k-2))
y++;
else
{
y=0;
x++;
}
}
}
}
deter=deter + z * (matrix[0][a] * determin(mt,k-1));
z=-1 *
z;
}
}
return(deter);
}
void cofac(float
comatr[40][40], int f){
float
matr[40][40], cofact[40][40];
int a,
b, c, d, x, y;
for(c=0; c<f; ++c){
for(d=0; d<f; ++d){
x=0;
y=0;
for(a=0;a<f; ++a){
for(b=0; b<f; ++b){
if(a !=
c && b != d)
{
matr[x][y]=comatr[a][b];
if(y<(f-2))
y++;
else
{
y=0;
x++;
}
}
}
}
cofact[c][d] = pow(-1,c + d) * determin(matr,f-1);
}
}
trans(comatr, cofact, f);
}
void trans(float
matr[40][40], float m1[40][40], int r){
float
inv_matrix[40][40], tran[40][40], d;
int a,b;
for(a=0;a<r;++a){
for(b=0;b<r;++b){
tran[a][b]=m1[b][a];
}
}
d=determin(matr, r);
for(a=0;a<r;++a){
for(b=0;b<r;++b){
inv_matrix[a][b]=tran[a][b] / d;
}
}
printf("\n\n\n The Inverse of matrix is :\n\n");
for(a=0;a<r;++a){
for(b=0;b<r;++b)
printf("\t%f", inv_matrix[a][b]);
printf("\n\n");
}
}
OUTPUT
