hdu 3308 线段树

写给自己看，记自己错的几个点

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
#include <iostream>
using namespace std;
typedef long long ll;
const int MAXN = int (1e5) + 5;
const int INF = (1 << 30);
#define lson rt << 1, l, m
#define rson rt << 1 | 1, m + 1, r
#define rclen (curlen >> 1)
#define lclen (curlen - rclen)
#define getMid ((l + r) >> 1)
int arr[MAXN];
int llen[MAXN << 2];
int rlen[MAXN << 2];
int maxlen[MAXN << 2];
void push_up(int rt, int l, int r)
{
	int curlen = r - l + 1;
	llen[rt] = llen[rt << 1];
	rlen[rt] = rlen[rt << 1 | 1];
	maxlen[rt] = max(maxlen[rt << 1], maxlen[rt << 1 | 1]);//不是max(llen[rt], rlen[rt])
	int m = getMid;
	if (arr[m] < arr[m + 1])
	{
		if (llen[rt] == lclen)
			llen[rt] += llen[rt << 1 | 1];
		if (rlen[rt] == rclen)
			rlen[rt] += rlen[rt << 1];
		int t = rlen[rt << 1] + llen[rt << 1 | 1];
		maxlen[rt] = max(t, max(maxlen[rt << 1], maxlen[rt << 1 | 1]));//不是max(t, max(llen[rt], rlen[rt]))
	}
}

void build(int rt, int l, int r)
{
	if (l == r)
	{
		scanf("%d", &arr[l]);
		llen[rt] = rlen[rt] = maxlen[rt] = 1;
		return;
	}
	int m = getMid;
	build(lson);
	build(rson);
	push_up(rt, l, r);
}

void updata(int val, int L, int R, int rt, int l, int r)
{
	if (L <= l && r <= R)
	{
		arr[l] = val;
		llen[rt] = rlen[rt] = maxlen[rt] = 1;
		return;
	}
	int m = getMid;
	if (L <= m)
		updata(val, L, R, lson);
	if (R > m)
		updata(val, L, R, rson);
	push_up(rt, l, r);
}

int query(int L, int R, int rt, int l, int r)
{
	if (L <= l && r <= R)
		return maxlen[rt];
	int m = getMid;
	int a = 0, b = 0;
	if (L <= m)
		a = query(L, R, lson);
	if (R > m)
		b = query(L, R, rson);
	int ans = max(a, b);//不是相加
	if (arr[m] < arr[m + 1])
	{
		int t = min(rlen[rt << 1], m - L + 1) + min(llen[rt << 1 | 1], R - m); //两个min是确保查询范围不越界
		ans = max(ans, t);
	}
	return ans;
}

int main(void)
{
	freopen("in.txt", "r", stdin);
	freopen("out.txt", "w", stdout);
	/*ios::sync_with_stdio(false);
	cin.tie(0);*/
	char op[2];
	int T, n, m, a, b;
	scanf("%d", &T);
	while (T--)
	{
		scanf("%d %d", &n, &m);
		build(1, 0, n - 1);
		while (m--)
		{
			scanf("%s %d %d", op, &a, &b);
			if (op[0] == 'Q')
				printf("%d\n", query(a, b, 1, 0, n - 1));
			else
				updata(b, a, a, 1, 0, n - 1);
		}
	}
	return 0;
}