why this is not giving the correct sum of a given matrix?

Question

this is the code.

#include <iostream>

using namespace std;

int main() {
int arr[5][5] =
{
{1,2,3,4,5},
{6,7,8,9,10},
{11,12,13,14,15},
{16,17,18,19,20},
{21,22,23,24,25}
};
int csum=0;
for(int i=0;i<5;i++) {
for(int j=0;j<5;j++) {
csum += arr[i][j];
}
}
int checksum=0;
for(int i=1;i<=20;i++)
checksum += i;
cout << "it should be : " << checksum << endl;
cout << "it is : " << csum << endl;
}

Answer 1

Sum of first 25 numbers = 25*13.

The second loop calculates sum from 1 to 20, as opposed to the matrix which calculates from 1 to 25.

Thats why (checksum!=csum) is true.

Answer 2

that was a silly mistake. Anyways thnx for your help as always.

Answer 3

Glad that I could help...