POJ2104 K-th Number(归并树)

平方分割一直TLE，最后用归并树处理过了，使用STL会比较慢。

#include<cstdio>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<string>
#include<algorithm>
#include<map>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
using namespace std;
typedef long long LL;
#define lson l, mid, rt << 1
#define rson mid + 1, r, rt << 1 | 1

const int N = 100008, INF = 0x3F3F3F3F;
int tp[N], a[N];
vector<int> v[N << 2];

void build(int l, int r, int rt){
	if(l == r){
		v[rt].clear();
		v[rt].push_back(a[l]);
	}else{
	    int mid = (l + r) >> 1;
		build(lson);
		build(rson);
		v[rt].resize(r - l + 1);
		merge(v[rt << 1].begin(), v[rt << 1].end(), v[rt << 1 | 1].begin(), v[rt << 1 | 1].end(), v[rt].begin());
	}
}

int query(int a, int b, int l, int r, int rt, int x){
    if(a <= l && b >= r){
		return upper_bound(v[rt].begin(), v[rt].end(), x) - v[rt].begin();
	}

	int mid = (l + r) >> 1;
	int cnt = 0;
	if(a <= mid){
		cnt += query(a, b, lson, x);
	}
	if(b > mid){
		cnt += query(a, b, rson, x);
	}
	return cnt;
}

int main(){
    int n, q;
    while(~scanf("%d %d", &n, &q)){
    	for(int i = 0; i < n; i++){
    		scanf("%d", &a[i]);
    		tp[i] = a[i];
    	}
    	build(0, n - 1, 1);
    	sort(tp, tp + n);
    	int cnt = unique(tp, tp + n) - tp;
    	while(q--){
    		int a, b, k;
    		scanf("%d %d %d", &a, &b, &k);
    		a--;
    		b--;
    		int l = 0, r = cnt;
    		while(l < r){
    			int mid = (l + r ) >> 1;
    			if(query(a, b, 0, n - 1, 1, tp[mid]) < k){
    				l = mid + 1;
    			}else{
    				r = mid;
    			}
    		}
    		printf("%d\n", tp[l]);
    	}

    }

    return 0;
}