P3834 【模板】可持久化线段树 1（主席树）

P3834 【模板】可持久化线段树 1（主席树）

#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e5+5;
int n, q, m, cnt = 0;
int a[maxn], b[maxn], T[maxn];
int sum[maxn<<5], L[maxn<<5], R[maxn<<5];
inline int build(int l, int r) {
    int rt = ++cnt;
    sum[rt] = 0;
    if (l < r) {
        int mid = (l+r)/2;
        L[rt] = build(l, mid);
        R[rt] = build(mid+1, r);
    }
    return rt;
}
inline int update(int pre, int l, int r, int x) {
    int rt = ++cnt;
    L[rt] = L[pre]; R[rt] = R[pre]; sum[rt] = sum[pre]+1;
    if (l < r) {
        int mid = (l+r)/2;
        if (x <= mid) L[rt] = update(L[pre], l, mid, x);
        else R[rt] = update(R[pre], mid+1, r, x);
    }
    return rt;
}
inline int query(int u, int v, int l, int r, int k) {
    if (l >= r) return l;
    int x = sum[L[v]] - sum[L[u]];
    int mid = (l+r)/2;
    if (x >= k) return query(L[u], L[v], l, mid, k);
    else return query(R[u], R[v], mid+1, r, k-x);
}
int main() {
    scanf("%d%d",&n,&q);
    for (int i = 1; i <= n; ++i) {
        scanf("%d",&a[i]);
        b[i] = a[i];
    }
    sort(b+1,b+1+n);
    m = unique(b+1,b+1+n)-b-1;
    T[0] = build(1,m);
    for (int i = 1; i <= n; ++i) {
        int t = lower_bound(b+1,b+1+m,a[i])-b;
        T[i] = update(T[i-1], 1, m, t);
    }
    while (q--) {
        int l, r, k;
        scanf("%d%d%d",&l,&r,&k);
        int t = query(T[l-1], T[r], 1, m, k);
        printf("%d\n",b[t]);
    }
    return 0;
}