Poj3667Hotel线段树

 区间合并。

需要记录三个东西，sum[rt] 表示这个区间最长连续空集的长度，lsum[rt]=表示从左边开始最长连续空集的长度，rum[rt]表示从右边最长连续空集的长度。

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <climits>

#include <string>

#include <iostream>

#include <map>

#include <cstdlib>

#include <list>

#include <set>

#include <queue>

#include <stack>

#include<math.h>

using namespace std;

#define lson l,mid,rt<<1

#define rson mid+1,r,rt<<1|1

const int maxn = 55555;

int color[maxn << 2];

int sum[maxn << 2], lsum[maxn << 2], rsum[maxn << 2];



void down(int rt, int m)

{

    if (~color[rt]){

        color[rt << 1] = color[rt << 1 | 1] = color[rt];

        sum[rt << 1] = lsum[rt << 1] = rsum[rt << 1] = color[rt] ? 0 : (m - (m >> 1));

        sum[rt << 1 | 1] = lsum[rt << 1 | 1] = rsum[rt << 1 | 1] = color[rt] ? 0 : (m >> 1);

        color[rt] = -1;

    }

}





void up(int rt, int m)

{

    lsum[rt] = lsum[rt << 1];

    rsum[rt] = rsum[rt << 1 | 1];

    if (lsum[rt] == (m - (m >> 1))) lsum[rt] += lsum[rt << 1 | 1];

    if (rsum[rt] == (m >> 1)) rsum[rt] += rsum[rt << 1];

    sum[rt] = max(rsum[rt << 1] + lsum[rt << 1 | 1], max(sum[rt << 1], sum[rt << 1 | 1]));//这里就是很神，不知道怎么想到的，用这三个量就可以记录更新区间最长连续0。sum的大小只和左右儿子的sum，和横跨左右儿子的那一部分有关。

}



void build(int l, int r, int rt)

{

    color[rt] = -1; sum[rt] = lsum[rt] = rsum[rt] = r - l + 1;

    if (l == r) return;

    int mid = (l + r) >> 1;

    build(lson);

    build(rson);

}



void update(int L, int R, int add, int l, int r, int rt)

{

    if (L <= l&&r <= R){

        sum[rt] = lsum[rt] = rsum[rt] = add ? 0 : r - l + 1;

        color[rt] = add; return;

    }

    down(rt, r - l + 1);

    int mid = (l + r) >> 1;

    if (L <= mid) update(L, R, add, lson);

    if (R>mid) update(L, R, add, rson);

    up(rt, r - l + 1);

}



int ask(int key, int l, int r, int rt)

{

    if (l == r) return l;

    int mid = (l + r) >> 1;

    down(rt, r - l + 1);

    if (sum[rt << 1] >= key) return ask(key, lson);

    else if (rsum[rt << 1] + lsum[rt << 1 | 1] >= key) return mid - rsum[rt << 1] + 1;

    return ask(key, rson);

}



int main()

{

    int n, m;

    int a, b, c;

    while (cin >> n >> m){

        build(1, n, 1);

        for (int i = 0; i < m; i++){

            scanf("%d", &a);

            if (a == 1){

                scanf("%d", &b);

                if (b>sum[1]){

                    printf("0\n"); continue;

                }

                int pos = ask(b, 1, n, 1);

                printf("%d\n", pos);

                update(pos, pos + b - 1, 1, 1, n, 1);

            }

            else{

                scanf("%d%d", &b, &c);

                update(b, b + c - 1, 0, 1, n, 1);

            }

        }

    }

    return 0;

}