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HDU 2665 Kth number 主席樹裸題

編輯：C++入門知識

HDU 2665 Kth number 主席樹裸題

主席樹詳解

每次插入logn個點這樣就不需要重新建樹了。

#pragma comment(linker, /STACK:1024000000,1024000000)  
#include 
#include 
#include 
#include 
#include 
#include
#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
template 
inline bool rd(T &ret) {
	char c; int sgn;
	if (c = getchar(), c == EOF) return 0;
	while (c != '-' && (c<'0' || c>'9')) c = getchar();
	sgn = (c == '-') ? -1 : 1;
	ret = (c == '-') ? 0 : (c - '0');
	while (c = getchar(), c >= '0'&&c <= '9') ret = ret * 10 + (c - '0');
	ret *= sgn;
	return 1;
}
template 
inline void pt(T x) {
	if (x < 0) {
		putchar('-');
		x = -x;
	}
	if (x > 9) pt(x / 10);
	putchar(x % 10 + '0');
}
typedef long long ll;
typedef pair pii;
const int N = 100000 + 100;
#define L(x) tree[x].lson
#define R(x) tree[x].rson
#define S(x) tree[x].sum
struct Node {
	int lson, rson;
	int sum;
}tree[N << 5];
int top;
vectorHash;
int gethash(int val) {
	return lower_bound(Hash.begin(), Hash.end(), val) - Hash.begin() + 1;
}
int build(int l, int r) {
	int id = ++top;
	S(id) = 0;
	if (l < r) {
		int mid = (l + r) >> 1;
		L(id) = build(l, mid);
		R(id) = build(mid + 1, r);
	}
	return id;
}
int update(int pre, int l, int r, int val) {
	int id = ++top;
	L(id) = L(pre); R(id) = R(pre);
	S(id) = S(pre) + 1;
	if (l < r) {
		int mid = (l + r) >> 1;
		if (val <= mid)
			L(id) = update(L(pre), l, mid, val);
		else
			R(id) = update(R(pre), mid + 1, r, val);
	}
	return id;
}
int query(int old, int cur, int l, int r, int k) {
	if (l >= r)return l;
	int mid = (l + r) >> 1;
	int siz = S(L(cur)) - S(L(old));
	if (siz < k)
		return query(R(old), R(cur), mid + 1, r, k - siz);
	else
		return query(L(old), L(cur), l, mid, k);
}
int n, q;
int a[N];
int T[N];
int main() {
	int cas; rd(cas);
	while (cas--) {
		rd(n); rd(q);
		Hash.clear();
		top = 0;
		for (int i = 1; i <= n; i++) {
			rd(a[i]);
			Hash.push_back(a[i]);
		}
		sort(Hash.begin(), Hash.end()); Hash.erase(unique(Hash.begin(), Hash.end()), Hash.end());
		T[0] = build(1, Hash.size());
		for (int i = 1; i <= n; i++) {
			T[i] = update(T[i - 1], 1, Hash.size(), gethash(a[i]));
		}
		while (q--) {
			int l, r, k;
			rd(l); rd(r); rd(k);
			int id = query(T[l - 1], T[r], 1, Hash.size(), k);
			pt(Hash[id - 1]); puts();
		}
	}
	return 0;
}