权值线段树

动态开点

题目链接

#include <bits/stdc++.h>
#define ll long long
#define mid (l+r>>1)
using namespace std;
const int N = 1e5+100;
const ll inf = 1e10+10;
ll L,R;
int n, tot;
int rt, ls[N*40], rs[N*40], tree[N*40];  //需要开N*log(maxlen)的空间,N为插入的点数
void insert(int &o, ll l, ll r, ll data) {    //插入一个权值data
    if(!o) o = ++tot;
    tree[o]++;
    if(l == r) return ;
    if(data <= mid) insert(ls[o], l, mid, data);
    else insert(rs[o], mid+1, r, data);
}
ll query(int o, ll l, ll r, ll h, ll t) {    //查询区间和
    if(h <= l && t >= r) return tree[o];
    if(t < l || h > r) return 0;
    return query(ls[o], l, mid, h, t) + query(rs[o], mid+1, r, h, t);
}
int main() {
    freopen("a.txt","r",stdin);
    ios::sync_with_stdio(0);
    cin>>n>>L>>R;
    ll sum = 0;
    ll ans = 0;
    insert(rt,-inf,inf,0); //插入这个0是为了满足题目需求
    for(int i = 1; i <= n; i++) {
        ll x;
        cin>>x;
        sum += x;
        ans += query(rt,-inf,inf,sum-R,sum-L);
        insert(rt,-inf,inf,sum);
    }
    cout<<ans;
    return 0;

}