50202. Diamond

#include <stdio.h>
#include <stdlib.h>
#include <limits.h>

#define max(a,b) ((a)>(b)?(a):(b))

int h, w, k;
int arr[256][256] = {0};

int get_sum(int x, int y){
    int ans = 0;
    for(int i = -k + 1; i < k; i++){
        int j = k - abs(i) - 1;
        if(j == 0) ans += arr[x + i][y + j];
        else ans += arr[x + i][y - j] + arr[x + i][y + j];
    }
    return ans;
}

int main(){
    scanf("%d %d %d", &h, &w, &k);
    for(int i = 0; i < h; i++){
        for(int j = 0; j < w; j++){
            scanf("%d", &arr[i][j]);
        }
    }

    int max_num = INT_MIN;
    for(int i = k - 1; i <= h - k; i++){
        for(int j = k - 1; j <= w - k; j++){
            max_num = max(max_num, get_sum(i, j));
        }
    }
    printf("%d\n", max_num);
}