HDU 5443 The Water Problem （线段树）

题意：给出n个数字，q个查询，查询l~r中最大的数。

题解：线段树

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<cstdio>
#include<string>
#include<cstring>
#include<algorithm>
#include<queue>
#include<stack>
#include<cmath>
#include<vector>
#include<fstream>
#include<set>
#include<map>
#include<sstream>
#include<iomanip>
#define ll long long
using namespace std;
const int maxn = 1111;
int t, n, q, a[maxn], l, r;
struct node {
	int val;
};
struct ST {
	node tree[maxn << 2];
	void build(int l, int r, int rt) {
		if (l == r) {
			tree[rt].val = a[l];
		}
		else {
			int mid = (l + r) >> 1;
			build(l, mid, rt << 1);
			build(mid + 1, r, rt << 1 | 1);
			tree[rt].val = max(tree[rt << 1].val, tree[rt << 1 | 1].val);
		}
	}
	int query(int l, int r, int L, int R, int rt) {    //L R 为查询区间
		if (L <= l && r <= R) {  //单点查询 l == r
			return tree[rt].val;
		}
		int mid = (l + r) >> 1;
		int ans1 = 0;
		if (L <= mid) {
			ans1 = query(l, mid, L, R, rt << 1);
		}
		if (R > mid) {
			ans1 = max(ans1, query(mid + 1, r, L, R, rt << 1 | 1));
		}
		return ans1;
	}
}stree;

int main() {
	scanf("%d", &t);
	while (t--) {
		scanf("%d", &n);
		for (int i = 1; i <= n; i++) scanf("%d", &a[i]);
		stree.build(1, n, 1);
		scanf("%d", &q);
		while (q--) {
			scanf("%d%d", &l, &r);
			printf("%d\n", stree.query(1, n, l, r, 1));
		}
	}
	return 0;
}