牛妹吃豆子 二维差分 二维前缀和

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code

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll N = 2e3+5;
ll n, m, k, q;
ll d[N][N], sum[N][N];
int main()
{
    scanf("%lld%lld%lld%lld", &n, &m, &k, &q);
    while(k--)
    {
        ll x1, y1, x2, y2;
        scanf("%lld%lld%lld%lld", &x1, &y1, &x2, &y2);
        d[x1][y1]++;
        d[x1][y2+1]--;
        d[x2+1][y1]--;
        d[x2+1][y2+1]++;
    }
    for(ll i = 1; i <= n; i++)
        for(ll j = 1; j <= m; j++)
            d[i][j] += d[i-1][j] + d[i][j-1] - d[i-1][j-1];
    for(ll i = 1; i <= n; i++)
        for(ll j = 1; j <= m; j++)
            sum[i][j] = sum[i-1][j] + sum[i][j-1] - sum[i-1][j-1] + d[i][j];
    while(q--)
    {
        ll x1, y1, x2, y2;
        scanf("%lld%lld%lld%lld", &x1, &y1, &x2, &y2);
        printf("%lld\n", sum[x2][y2] - sum[x1-1][y2] - sum[x2][y1-1] + sum[x1-1][y1-1]);
    }
    return 0; 
}