HDU 5443 The Water Problem 线段树找区间内最大值

HDU 5443 The Water Problem

解题思路：线段树找区间内最大值，线段树基础题，这题用来练练敲线段树板子还是挺不错的。

#include<iostream>
#include<math.h>
#include<iomanip>
#include<algorithm>
#include<iostream>
#include<math.h>
#include<iomanip>
#include<algorithm>
#include<queue>
#include<cstring>
#include<string>
#include<map>
#include<stack>
#include<stdio.h>
#include<cstdio>
#include<stdlib.h>
#include<fstream>
#include<iomanip>
#pragma warning(disable:4996)
#define INF 0x3f3f3f3f
#define ll long long
#define PI acos(-1.0)
const int N = 1000010;
const int maxn = 1e9;
using namespace std;
int tree[4005];
int a[1005];
int n, q;
void build(int id, int l, int r)
{
	if (l == r)
	{
		tree[id] = a[l];
		return;
	}
	int mid = (l + r) >> 1;
	build(id << 1, l, mid);
	build(id << 1 | 1, mid + 1, r);
	tree[id] = max(tree[id << 1], tree[id << 1 | 1]);
}
int query(int id, int l, int r, int x, int y)
{
	if (x <= l && y >= r)
	{
		return tree[id];
	}
	int mid = (l + r) >> 1;
	int res = 0;
	if (x <= mid)
	{
		res = max(query(id << 1, l, mid, x, y), res);
	}
	if (y > mid)
	{
		res = max(query(id << 1 | 1, mid + 1, r, x, y), res);
	}
	return res;
}
int main()
{
	int t;
	scanf("%d", &t);
	while (t--)
	{
		memset(a, 0, sizeof(a));
		memset(tree, 0, sizeof(tree));
		scanf("%d", &n);
		for (int i = 1; i <= n; i++)
		{
			scanf("%d", &a[i]);
		}
		build(1, 1, n);
		scanf("%d", &q);
		for (int i = 1; i <= q; i++)
		{
			int l, r;
			scanf("%d%d", &l, &r);
			printf("%d\n", query(1, 1, n, l, r));
		}
	}
}