Codeforces Round #817 (Div. 4)E Counting Rectangles

Counting Rectangles

思维

把所有的矩形左上角都叠在一起，就会发现是一个二维前缀和的求解问题：\(\sum_{i=h_s+1}^{h_b-1} \sum_{j=w_s+1}^{w_b-1} (i*j*cnt_{ij})\)

这个显然就是一个二维前缀和的问题，直接算就好了

#include <iostream>
#include <cstdio>
#include <string>
#include <map>
#include <algorithm>
#include <vector>
using namespace std;
typedef long long ll;
const int maxn = 1010;
ll num[maxn][maxn], sum[maxn][maxn];

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t;
    cin >> t;
    while(t--)
    {
        int n, m;
        cin >> n >> m;
        ll max_s = 0, max_w = 0;
        for(int i=0; i<n; i++)
        {
            ll a, b;
            cin >> a >> b;
            max_s = max(a, max_s);
            max_w = max(b, max_w);
            num[a][b] += a * b;
        }
        for(int i=1; i<maxn; i++)
        {
            ll temp = 0;
            for(int j=1; j<maxn; j++)
            {
                temp += num[i][j];
                sum[i][j] = sum[i-1][j] + temp;
            }
        }
        for(int i=0; i<=max_s; i++)
            for(int j=0; j<=max_w; j++)
                num[i][j] = 0;
        while(m--)
        {
            ll a, b, c, d;
            cin >> a >> b >> c >> d;
            ll ans = sum[c - 1][d - 1];
            ans -= sum[a][d - 1] + sum[c - 1][b];
            ans += sum[a][b];
            cout << ans << "\n";
        }
    }
    // cout << endl;
    return 0;
}

标签：include,int,max,sum,Codeforces,maxn,Div,Counting,ll
来源： https://www.cnblogs.com/dgsvygd/p/16641712.html