POJ 1823 Hotel 线段树

#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <queue>
using namespace std;
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
const int maxn = 16005;
int maxx[maxn<<2], pre_max[maxn<<2], suf_max[maxn<<2], cover[maxn<<2];
void pushUp(int rt, int m) {
    maxx[rt] = max(maxx[rt<<1], maxx[rt<<1|1]);
    pre_max[rt] = pre_max[rt<<1];
    suf_max[rt] = suf_max[rt<<1|1];
    if(maxx[rt<<1] == (m-(m>>1)))
        pre_max[rt] = pre_max[rt<<1] + pre_max[rt<<1|1];
    if(maxx[rt<<1|1] == (m>>1))
        suf_max[rt] = suf_max[rt<<1|1]+suf_max[rt<<1];
    maxx[rt] = max(maxx[rt], suf_max[rt<<1]+pre_max[rt<<1|1]);
}
void build(int l, int r, int rt) {
    maxx[rt] = pre_max[rt] = suf_max[rt] = r-l+1;
    cover[rt] = -1;
    if(l == r)
        return ;
    int m = l+r>>1;
    build(lson);
    build(rson);
}
void pushDown(int rt, int m) {
    if(~cover[rt]) {
        cover[rt<<1] = cover[rt<<1|1] = cover[rt];
        maxx[rt<<1] = pre_max[rt<<1] = suf_max[rt<<1] = cover[rt]*(m-(m>>1));
        pre_max[rt<<1|1] = suf_max[rt<<1|1] = maxx[rt<<1|1] = cover[rt]*(m>>1);
        cover[rt] = -1;
    }
}
void update(int L, int R, int l, int r, int rt, int val) {
    if(L<=l&&R>=r) {
        cover[rt] = val;
        maxx[rt] = suf_max[rt] = pre_max[rt] = val*(r-l+1);
        return ;
    }
    pushDown(rt, r-l+1);
    int m = l+r>>1;
    if(L<=m)
        update(L, R, lson, val);
    if(R>m)
        update(L, R, rson, val);
    pushUp(rt, r-l+1);
}
int main()
{
    int n, m, sign, x, y;
    while(cin>>n>>m) {
        build(1, n, 1);
        while(m--) {
            scanf("%d", &sign);
            if(sign == 1) {
                scanf("%d%d", &x, &y);
                update(x, y+x-1, 1, n, 1, 0);
            } else if(sign == 2){
                scanf("%d%d", &x, &y);
                update(x, y+x-1, 1, n, 1, 1);
            } else {
                printf("%d\n", maxx[1]);
            }
        }
    }
}