POJ 3667 Hotel

题目链接

题意：有n个房间，如今有两个操作
1、找到连续长度a的空房间。入住，要尽量靠左边，假设有输出最左边的房间标号，假设没有输出0
2、清空[a, a + b - 1]的房间

思路：线段树的区间合并。记录下左边连续最长和右边连续最长空房间。和每一段的最大值。这样pushup的时候就是进行区间合并，注意查询的时候因为是要尽量左，所以先查左孩子，在查横跨左右的，在查右孩子

代码：

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;#define lson(x) ((x<<1)+1)
#define rson(x) ((x<<1)+2)const int N = 50005;int n, m;struct Node {int l, r, lsum, rsum, sum, sumv, lazy;int size() {return r - l + 1;}void gao(int v) {lazy = v;if (v) lsum = rsum = sum = 0;else lsum = rsum = sum = r - l + 1;sumv = l;}
} node[N * 4];void pushup(int x) {if (node[lson(x)].lsum == node[lson(x)].size()) node[x].lsum = node[lson(x)].lsum + node[rson(x)].lsum;else node[x].lsum = node[lson(x)].lsum;if (node[rson(x)].rsum == node[rson(x)].size()) node[x].rsum = node[lson(x)].rsum + node[rson(x)].rsum;else node[x].rsum = node[rson(x)].rsum;node[x].sum = node[lson(x)].sum;node[x].sumv = node[lson(x)].sumv;if (node[x].sum < node[lson(x)].rsum + node[rson(x)].lsum) {node[x].sum = node[lson(x)].rsum + node[rson(x)].lsum;node[x].sumv = node[lson(x)].r - node[lson(x)].rsum + 1;}if (node[x].sum < node[rson(x)].sum) {node[x].sum = node[rson(x)].sum;node[x].sumv = node[rson(x)].sumv;}
}void pushdown(int x) {if (node[x].lazy != -1) {node[lson(x)].gao(node[x].lazy);node[rson(x)].gao(node[x].lazy);node[x].lazy = -1;}
}void build(int l, int r, int x = 0) {node[x].l = l; node[x].r = r; node[x].lazy = -1;if (l == r) {node[x].lsum = node[x].rsum = node[x].sum = 1;return;}int mid = (l + r) / 2;build(l, mid, lson(x));build(mid + 1, r, rson(x));pushup(x);
}void add(int l, int r, int v, int x = 0) {if (node[x].l >= l && node[x].r <= r) {node[x].gao(v);return;}int mid = (node[x].l + node[x].r) / 2;pushdown(x);if (l <= mid) add(l, r, v, lson(x));if (r > mid) add(l, r, v, rson(x));pushup(x);
}int query(int v, int x = 0) {if (node[x].l == node[x].r) {if (node[x].sum >= v) return node[x].sumv;return 0;}pushdown(x);int ans = 0;if (node[lson(x)].sum >= v)ans = query(v, lson(x));else if (node[lson(x)].rsum + node[rson(x)].lsum >= v) ans = node[lson(x)].r - node[lson(x)].rsum + 1;else if (node[rson(x)].sum >= v)ans = query(v, rson(x));pushup(x);return ans;
}int main() {while (~scanf("%d%d", &n, &m)) {build(1, n);int op, a, b;while (m--) {scanf("%d%d", &op, &a);if (op == 2) {scanf("%d", &b);add(a, a + b - 1, 0);} else {int tmp = query(a);printf("%d\n", tmp);if (tmp == 0) continue;add(tmp, tmp + a - 1, 1);}}}return 0;
}