C Beginner - 10 months ago 89

C Question

I'm trying to solve a matrix multiplication problem with C. Matrix sizes given in problem (2x2)

I wrote this code but it doesn't print result as I expect. I think I'm missing a point about rules of C.

What is my mistake in this code ?

`#include <stdio.h>`

int main() {

int matA[2][2]={0,1,2,3};

int matB[2][2]={0,1,2,3};

int matC[2][2];

int i, j, k;

for (i = 0; i < 2; i++) {

for(j = 0; j < 2; j++) {

for(k = 0; k < 2; k++) {

matC[i][j] += matA[i][k] * matB[k][j];

}

printf("%d\n",matC[i][j]);

}

}

}

Printing Result:

`2`

3

4195350

11

Answer

The problem is that in the line

```
matC[i][j] += matA[i][k] * matB[k][j];
```

you are adding things to matC, but when you create it, you don't initialize it, so it has garbage.

You sould do something like:

`int matC[2][2] = {0}`

which will initialize all the matrix with 0's

Source (Stackoverflow)