Why i am not getting the right answer?

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1

i was trying to make the program which takes two matrices as an input and display the multiplication of those two matrices but this program wasn,t giving the right answer

‘’’
#include
using namespace std;

int main() {
// your code goes here
int n1,n2,n3;
cin>>n1>>n2>>n3;

int a[n1][n2],b[n2][n3];

for(int i=0;i<n1;i++){
    for(int j=0;j<n2;j++){
        cin>>a[i][j];
        cout<<a[i][j]<<" ";
    }
    cout<<endl;
}

for(int i=0;i<n2;i++){
    for(int j=0;j<n3;j++){
        cin>>b[i][j];
        cout<<b[i][j]<<" ";
    }
    cout<<endl;
}


int c[n1][n3]={0};


for(int i=0;i<n1;i++){
    for(int j=0;j<n3;j++){
        for(int k=0;k<n2;k++){
            c[i][j]+=a[i][k]*b[k][j];
        }
        cout<<c[i][j]<<" ";
    }
    cout<<endl;
}


return 0;

}
‘’’

2

I made some changes in your soln now it is showing correct o/p

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n1,n2,n3;
cin>>n1>>n2>>n3;

int a[n1][n2],b[n2][n3],c[n1][n3];

for(int i=0;i<n1;i++){
    for(int j=0;j<n2;j++){
        cin>>a[i][j];
        cout<<a[i][j]<<" ";
    }
    cout<<endl;
}

for(int i=0;i<n2;i++){
    for(int j=0;j<n3;j++){
        cin>>b[i][j];
        cout<<b[i][j]<<" ";
    }
    cout<<endl;
}

//int c[n1][n3]={0};

for(int i=0;i<n1;i++){
    for(int j=0;j<n3;j++){
        c[i][j]=0;
        for(int k=0;k<n3;k++){
            c[i][j]+=a[i][k]*b[k][j];
        }
        cout<<c[i][j]<<" ";
    }
    cout<<endl;
}

return 0;
}
3

I didn’t get that. if I have already initialized the c array with 0 then why would I have to do it again in the loop

4

For initializing whole matrix with 0 you can use memset(c,0,sizeof(c)) instead of
c[i][j] = {0} as latter one can lead to wrong answer in online judge sometimes.

You can read more about the working of the latter syntax from here: c - Initializing entire 2D array with one value - Stack Overflow