一个简单的询问 HYSBZ - 5016

Posted 2020-11-28 晴屿

https://blog.csdn.net/weixin_30337251/article/details/99742674 参考文章

#include <bits/stdc++.h>
#define ll long long
#define inf 0x3f3f3f3f
#define N 50005
using namespace std;
struct node{
    int l, r, id, belong, k;
}q[N << 2];
int Dl[N], Dr[N], a[N];
ll res, ans[N];
int n, m, tot, belong;
bool cmp(node A, node B) 
{
    return (A.belong == B.belong)? (A.r < B.r): (A.belong < B.belong);
}
void AddL(int x) { res += Dr[a[x]]; ++ Dl[a[x]]; }
void AddR(int x) { res += Dl[a[x]]; ++ Dr[a[x]]; }
void DecL(int x) { res -= Dr[a[x]]; -- Dl[a[x]]; }
void DecR(int x) { res -= Dl[a[x]]; -- Dr[a[x]]; }
int main() {
    cin>>n; belong = sqrt(n);
    for (int i = 1; i <= n; i ++)
        cin>>a[i];
    cin>>m; 
    tot = 0;
    for (int i = 1; i <= m; i ++) {
        int l1, r1, l2, r2;
        cin>>l1>>r1>>l2>>r2;
        q[++ tot] = {l1 - 1, l2 - 1, i, (l1 - 2) / belong + 1, 1};
        q[++ tot] = {r1, r2, i, (r1 - 1) / belong + 1, 1};
        q[++ tot] = {l1 - 1, r2, i, (l1 - 2) / belong + 1, -1};
        q[++ tot] = {r1, l2 - 1, i, (r1 - 1) / belong + 1, -1};
    }
    sort(q + 1, q + 1 + tot, cmp);
    int l = 0, r = 0; 
    for (int i = 1; i <= tot; i ++) {
        while (r < q[i].r) 
            AddR(++ r);
        while (l > q[i].l) 
            DecL(l --);
        while (r > q[i].r) 
            DecR(r --);
        while (l < q[i].l) 
            AddL(++ l);
        ans[q[i].id] += q[i].k * res;
    }
    for (int i = 1; i <= m; i ++)   
        cout<<ans[i]<<endl;
    return 0;
}