Required output not displayed in sololearn c++ compiler.

Question

#include <iostream>
using namespace std;
//program to sum elements lying on any of the diagonal of matrix
int main()
{
int i,j,m,sum,ar[10][10];
cout<<"Enter number of columns\n";
cin>>m;
if(m>10)
{
cout<<"max(m)=10";
m=10;
}
for(i=0;i<m;i++)
{
for(j=0;j<m;j++)
{
ar[i][j]=1;
}
}
for(i=0;i<m;i++)
{
sum+=(ar[i][i]+ar[i][m-1-i]);
}
if(m%2==1)
sum-=ar[m/2][m/2];
cout<<sum;

return 0;
}

Answer 1

while declaring the variable "sum" initialize it as 0.
It will give you the desired output .
Hope it solves your problem.

Answer 2

To sum the elements of other diagonal.
let ar[3][3] be there.
first diagonal is ar[0][0],ar[1][1],ar[2][2]
second diagonal is ar[0][2],ar[1][1],ar[2][0]

Answer 3

Why do you sum diagonal like this: sum+=(ar[i][i]+ar[i][m-1-i]); ? sum+=ar[i][i]; is sufficient.