SCUT - 37 - 手速帝CZK - 分块

https://scut.online/p/37

一开始想到要根号分块预处理，但是不太懂具体怎么写。想不到如此暴力。

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MAXN = 300000;

//预留长出来的600
ll a[MAXN + 800 + 5];
ll res[MAXN + 800 + 5];
ll ans[MAXN + 800 + 5];

struct Query {
    int x, y, id;
} q;
vector<Query>v[800 + 5];

int main() {
    int n, m;
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= n; ++i)
        scanf("%lld", &a[i]);
    int block = (int)sqrt(n) + 200;
    for(int i = 1, x, y; i <= m; ++i) {
        scanf("%d%d", &x, &y);
        if(y > block) {
            //长度比较长，直接暴力统计
            for(int j = x; j <= n; j += y)
                ans[i] += a[j];
        } else {
            q.x = x, q.y = y, q.id = i;
            v[y].push_back(q);
        }
    }
    for(int y = block; y >= 1; --y) {
        for(int i = n; i >= 0; --i) {
            //暴力统计后缀和
            res[i] = a[i] + res[i + y];
        }
        int len = v[y].size();
        for(int i = 0; i < len; ++i)
            ans[v[y][i].id] = res[v[y][i].x];
    }
    for(int i = 1; i <= m; ++i)
        printf("%lld\n", ans[i]);
}