POJ 3667 Hotel 带区间合并操作的线段树
典型的带区间合并线段树，只要多加一个合并操作即可
Description
The cows are journeying north to Thunder Bay in Canada to gain cultural enrichment and enjoy a vacation on the sunny shores of Lake Superior. Bessie, ever the competent travel agent, has named the Bullmoose Hotel on famed Cumberland Street as their vacation residence. This immense hotel has N (1 ≤ N ≤ 50,000) rooms all located on the same side of an extremely long hallway (all the better to see the lake, of course).
The cows and other visitors arrive in groups of size Di (1 ≤ Di ≤ N) and approach the front desk to check in. Each group i requests a set of Di contiguous rooms from Canmuu, the moose staffing the counter. He assigns them some set of consecutive room numbers r..r+Di-1 if they are available or, if no contiguous set of rooms is available, politely suggests alternate lodging. Canmuu always chooses the value of r to be the smallest possible.
Visitors also depart the hotel from groups of contiguous rooms. Checkout i has the parameters Xi and Di which specify the vacating of rooms Xi ..Xi +Di-1 (1 ≤ Xi ≤ N-Di+1). Some (or all) of those rooms might be empty before the checkout.
Your job is to assist Canmuu by processing M (1 ≤ M < 50,000) checkin/checkout requests. The hotel is initially unoccupied.
Input
* Line 1: Two space-separated integers: N and M
* Lines 2..M+1: Line i+1 contains request expressed as one of two possible formats: (a) Two space separated integers representing a check-in request: 1 and Di (b) Three space-separated integers representing a check-out: 2, Xi, and Di
Output
* Lines 1.....: For each check-in request, output a single line with a single integer r, the first room in the contiguous sequence of rooms to be occupied. If the request cannot be satisfied, output 0.
Sample Input
10 6 1 3 1 3 1 3 1 3 2 5 5 1 6
Sample Output
1 4 7 0 5题意:
1 a:询问是不是有连续长度为a的空房间,返回最左边端点
2 a b:将[a,a+b-1]的房间清空
思路:线段记录区间中最长的空房间
线段树操作:update:区间替换 query:询问满足条件的最左端点
#include <cstdio>
#include <cstring>
#include <cctype>
#include <algorithm>
using namespace std;
#define lson l , m , rt << 1
#define rson m + 1 , r , rt << 1 | 1
const int maxn = 55555;
int lsum[maxn<<2] , rsum[maxn<<2] , msum[maxn<<2];
int cover[maxn<<2];
void PushDown(int rt,int m) {
if (cover[rt] != -1) {
cover[rt<<1] = cover[rt<<1|1] = cover[rt];
msum[rt<<1] = lsum[rt<<1] = rsum[rt<<1] = cover[rt] ? 0 : m - (m >> 1); /*左右端区间也要更新*/
msum[rt<<1|1] = lsum[rt<<1|1] = rsum[rt<<1|1] = cover[rt] ? 0 : (m >> 1); /*左右端区间也要更新*/
cover[rt] = -1;
}
}
void PushUp(int rt,int m) {
lsum[rt] = lsum[rt<<1]; /*区间合并步骤1*/
rsum[rt] = rsum[rt<<1|1]; /*区间合并步骤1*/
if (lsum[rt] == m - (m >> 1)) lsum[rt] += lsum[rt<<1|1]; /*区间合并步骤2*/
if (rsum[rt] == (m >> 1)) rsum[rt] += rsum[rt<<1]; /*区间合并步骤2*/
msum[rt] = max(lsum[rt<<1|1] + rsum[rt<<1] , max(msum[rt<<1] , msum[rt<<1|1])); /*总区间*/
}
void build(int l,int r,int rt) {
msum[rt] = lsum[rt] = rsum[rt] = r - l + 1; /*~~左右端区间也要更新*/
cover[rt] = -1;
if (l == r) return ;
int m = (l + r) >> 1;
build(lson);
build(rson);
}
void update(int L,int R,int c,int l,int r,int rt) {
if (L <= l && r <= R) {
msum[rt] = lsum[rt] = rsum[rt] = c ? 0 : r - l + 1; /*左右端区间也要更新*/
cover[rt] = c;
return ;
}
PushDown(rt , r - l + 1);
int m = (l + r) >> 1;
if (L <= m) update(L , R , c , lson);
if (m < R) update(L , R , c , rson);
PushUp(rt , r - l + 1);
}
int query(int w,int l,int r,int rt) {
if (l == r) return l;
PushDown(rt , r - l + 1);
int m = (l + r) >> 1;
if (msum[rt<<1] >= w) return query(w , lson);
else if (rsum[rt<<1] + lsum[rt<<1|1] >= w) return m - rsum[rt<<1] + 1; /*左子右 + 右子左 = 中间连续部分*/
return query(w , rson);
}
int main() {
int n , m;
scanf("%d%d",&n,&m);
build(1 , n , 1);
while (m --) {
int op , a , b;
scanf("%d",&op);
if (op == 1) {
scanf("%d",&a);
if (msum[1] < a) puts("0");
else {
int p = query(a , 1 , n , 1);
printf("%d\n",p);
update(p , p + a - 1 , 1 , 1 , n , 1);
}
} else {
scanf("%d%d",&a,&b);
update(a , a + b - 1 , 0 , 1 , n , 1);
}
}
return 0;
}