C and C++ Program to Find Inverse of a Matrix

Here you will get C and C++ program to find inverse of a matrix.

We can obtain matrix inverse by following method.

• First calculate deteminant of matrix.
• Then calculate adjoint of given matrix. Adjoint can be obtained by taking transpose of cofactor matrix of given square matrix.
• Finally multiply 1/deteminant by adjoint to get inverse.

The formula to find inverse of matrix is given below.

You can watch below video to learn how inverse is calculated.

In below program I have calculated the inverse of 3×3 matrix.

C Program to Find Inverse of a Matrix

#include<stdio.h>

int main(){
	int mat[3][3], i, j;
	float determinant = 0;
	
	printf("Enter elements of matrix row wise:\n");
	for(i = 0; i < 3; i++)
		for(j = 0; j < 3; j++)
           scanf("%d", &mat[i][j]);
	
	printf("\nGiven matrix is:");
	for(i = 0; i < 3; i++){
		printf("\n");
		
		for(j = 0; j < 3; j++)
			printf("%d\t", mat[i][j]);
	}
	
	//finding determinant
	for(i = 0; i < 3; i++)
		determinant = determinant + (mat[0][i] * (mat[1][(i+1)%3] * mat[2][(i+2)%3] - mat[1][(i+2)%3] * mat[2][(i+1)%3]));
	
	printf("\n\ndeterminant: %f\n", determinant);
	
	printf("\nInverse of matrix is: \n");
	for(i = 0; i < 3; i++){
		for(j = 0; j < 3; j++)
			printf("%.2f\t",((mat[(j+1)%3][(i+1)%3] * mat[(j+2)%3][(i+2)%3]) - (mat[(j+1)%3][(i+2)%3] * mat[(j+2)%3][(i+1)%3]))/ determinant);
		
		printf("\n");
	}

   return 0;
}

C++ Program to Find Inverse of a Matrix

#include<iostream>

using namespace std;

int main(){
	int mat[3][3], i, j;
	float determinant = 0;
	
	cout<<"Enter elements of matrix row wise:\n";
	for(i = 0; i < 3; i++)
		for(j = 0; j < 3; j++)
           cin>>mat[i][j];
	
	printf("\nGiven matrix is:");
	for(i = 0; i < 3; i++){
		cout<<"\n";
		
		for(j = 0; j < 3; j++)
			cout<<mat[i][j]<<"\t";
	}
	
	//finding determinant
	for(i = 0; i < 3; i++)
		determinant = determinant + (mat[0][i] * (mat[1][(i+1)%3] * mat[2][(i+2)%3] - mat[1][(i+2)%3] * mat[2][(i+1)%3]));
	
	cout<<"\n\ndeterminant: "<<determinant;
	
	cout<<"\n\nInverse of matrix is: \n";
	for(i = 0; i < 3; i++){
		for(j = 0; j < 3; j++)
			cout<<((mat[(j+1)%3][(i+1)%3] * mat[(j+2)%3][(i+2)%3]) - (mat[(j+1)%3][(i+2)%3] * mat[(j+2)%3][(i+1)%3]))/ determinant<<"\t";
		
		cout<<"\n";
	}

   return 0;
}

Output

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