HDU2665 （主席树）

主席树板子

#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <string>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
#include <bitset>
using namespace std;

typedef long long ll;
//#define int ll
#define INF 0x3f3f3f3f3f3f3f3f
#define MAXM 2000000 + 10
#define MAXN 100000 + 10
const ll mod = 1e9 + 7;
#define fir first
#define sec second

int cas, n, m;
int a[MAXN], cp[MAXN];
int rt[MAXM], cnt;
struct node {
    int l, r;
    int sum;
}tree[MAXM];

void build(int &now, int l, int r)
{
    now = ++cnt;
    tree[now].sum = 0;
    if(l == r) return ;
    int mid = (l + r) >> 1;
    build(tree[now].l, l, mid);
    build(tree[now].r, mid + 1, r);
}

void update(int &now, int c, int l, int r, int pre)
{
    now = ++cnt;
    tree[now].sum = tree[pre].sum + 1;
    tree[now].l = tree[pre].l;
    tree[now].r = tree[pre].r;
    if(l == r) return ;
    int mid = (l + r) >> 1;
    if(c <= mid) update(tree[now].l, c, l, mid, tree[pre].l);
    else update(tree[now].r, c, mid + 1, r, tree[pre].r);
}

int query(int L, int R, int l, int r, int k)
{
    if(l == r) return l;
    int num = tree[tree[R].l].sum - tree[tree[L].l].sum;
    int mid = (l + r) >> 1;
    if(num >= k) return query(tree[L].l, tree[R].l, l, mid, k);
    else return query(tree[L].r, tree[R].r, mid + 1, r, k - num);
}

int main()
{
    scanf("%d", &cas);
    while(cas --) {
        cnt = 0;
        scanf("%d %d", &n, &m);
        for(int i = 1; i <= n; i ++) scanf("%d", &a[i]), cp[i] = a[i];

        sort(cp + 1, cp + n + 1);
        int num = unique(cp + 1, cp + n + 1) - (cp + 1);
        for(int i = 1; i <= n; i ++)
            a[i] = lower_bound(cp + 1, cp + num + 1, a[i]) - cp;

        build(rt[0], 1, num);

        for(int i = 1; i <= n; i ++) {
            update(rt[i], a[i], 1, num, rt[i-1]);
        }

        for(int i = 0; i < m; i ++) {
            int s, t, k; scanf("%d %d %d", &s, &t, &k);
            int id = query(rt[s - 1], rt[t], 1, num, k);
            printf("%d\n", cp[id]);
        }
    }

}

/*

The WAM is F**KING interesting .

*/