TOI9: Fence

#include <bits/stdc++.h>
using namespace std;

const int N = 500;

int qsum[N + 1][N + 1];

int getSum(int x1, int y1, int x2, int y2){
    return qsum[x2][y2] - qsum[x1 - 1][y2] - qsum[x2][y1 - 1] + qsum[x1 - 1][y1 - 1];
}

int main(){

    int Q = 2;
    while(Q--){
        int row, col, nTree;
        scanf("%d%d%d", &row, &col, &nTree);
        for(int i = 1; i <= N; ++i){
            for(int j = 1; j <= N; ++j){
                qsum[i][j] = 0;
            }
        }
        for(int i = 1; i <= nTree; ++i){
            int r, c;
            scanf("%d%d", &r, &c);
            ++qsum[++r][++c];
        }
        for(int i = 1; i <= row; ++i){
            for(int j = 1; j <= col; ++j){
                qsum[i][j] += qsum[i - 1][j] + qsum[i][j - 1] - qsum[i - 1][j - 1];
            }
        }
        int mx = 0;
        for(int d = 1; d <= min(row, col); ++d){
            for(int i = 1; i <= row - d + 1; ++i){
                bool esc = false;
                for(int j = 1; j <= col - d + 1; ++j){
                    int ir = i + d - 1;
                    int jr = j + d - 1;
                    int ans = getSum(i, j, ir, jr) - ((d > 2) ? getSum(i + 1, j + 1, ir - 1, jr - 1) : 0);
                    if(ans == 0){
                        mx = max(mx, d);
                        esc = true;
                        break;
                    }
                }
                if(esc){
                    break;
                }
            }
        }
        cout << mx << '\n';
    }

    return 0;
}