108 - Maximum Sum

#include <iostream>#include <algorithm>#include <cstdlib>#include <cstring>#include <cstdio>#include <cctype>#include <cmath>using namespace std;int main(){    int a[130][130];    memset(a, 0, sizeof(a));    int n;    scanf("%d", &n);    for(int i = 0; i < n; i++)        for(int j = 0; j < n; j++)        {            scanf("%d",&a[i][j]);            if(i>0)            a[i][j]+=a[i-1][j];        }    int maxn = -1;    for(int i = 0; i < n; i++)        for(int j = i; j < n; j++)        {            int sum = 0;            for(int k = 0; k < n; k++)            {                if(sum < 0) sum = a[j][k] - a[i][k];                else if(i!=j) sum += a[j][k] - a[i][k];                if(sum > maxn && sum != 0) maxn = sum;            }        }    printf("%d\n", maxn);    return 0;}