线段树 区间合并

poj3667 Hotel

区间合并入门题，照着代码打的，

题意:1 a:询问是不是有连续长度为a的空房间,有的话住进最左边
       2 a b:将[a,a+b-1]的房间清空
思路:记录区间中最长的空房间，开三个数组，msum[rt]表示节点rt内连续的1的个数的最大值，lsum[rt]表示从节点rt左端点开始连续1的个数，rsum[rt]表示从节点rt右端点开始连续1的个数。。
线段树操作:update:区间替换 query:询问满足条件的最左端点

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 #include<algorithm>
 5 #include<string>
 6 #include<cmath>
 7 #include<map>
 8 #include<queue>
 9
10 using namespace std;
11
12 #define mnx 50005
13 #define Pi acos(-1.0)
14 #define ull unsigned long long
15 #define ll long long
16 #define inf 0x3f3f3f3f
17 #define eps 1e-8
18 #define MP make_pair
19 #define lson l, m, rt << 1
20 #define rson m+1, r, rt << 1 | 1
21 #define mod 2333333
22
23 int msum[mnx<<2], lsum[mnx<<2], rsum[mnx<<2], cover[mnx<<2];
24 void pushup( int rt, int m ){
25     lsum[rt] = lsum[rt<<1];
26     rsum[rt] = rsum[rt<<1|1];
27     if( lsum[rt] == m - ( m >> 1 ) ) lsum[rt] += lsum[rt<<1|1];
28     if( rsum[rt] == ( m >> 1 ) ) rsum[rt] += rsum[rt<<1];
29     msum[rt] = max( lsum[rt<<1|1] + rsum[rt<<1], max( msum[rt<<1], msum[rt<<1|1] ) );
30 }
31 void pushdown( int rt, int m ){
32     if( cover[rt] != -1 ){
33         cover[rt<<1] = cover[rt<<1|1] = cover[rt];
34         msum[rt<<1] = lsum[rt<<1] = rsum[rt<<1] = cover[rt] ? 0 : m - ( m >> 1 );
35         msum[rt<<1|1] = lsum[rt<<1|1] = rsum[rt<<1|1] = cover[rt] ? 0 : m >> 1;
36         cover[rt] = -1;
37     }
38 }
39 void build( int l, int r, int rt ){
40     msum[rt] = lsum[rt] = rsum[rt] = r - l + 1;
41     if( l == r ) return;
42     int m = ( l + r ) >> 1;
43     build( lson ); build( rson );
44 }
45 void update( int L, int R, int v, int l, int r, int rt ){
46     if( L <= l && R >= r ){
47         msum[rt] = rsum[rt] = lsum[rt] = v ? 0 : r - l + 1;
48         cover[rt] = v;
49         return ;
50     }
51     pushdown( rt, r - l + 1 );
52     int m = ( l + r ) >> 1;
53     if( L <= m ) update( L, R, v, lson );
54     if( R > m ) update( L, R, v, rson );
55     pushup( rt, r - l + 1 );
56 }
57 int query( int v, int l, int r, int rt ){
58     if( l == r ) return l;
59     pushdown( rt, r - l + 1 );
60     int m = ( l + r ) >> 1;
61     if( msum[rt<<1] >= v ) return query( v, lson );
62     else if( rsum[rt<<1] + lsum[rt<<1|1] >= v ) return m - rsum[rt<<1] + 1;
63     else return query( v, rson );
64 }
65 int main(){
66     int n, m;
67     while( scanf( "%d %d", &n, &m ) != EOF ){
68         memset( cover, -1, sizeof(cover) );
69         build( 1, n, 1 );
70         int op, a, b;
71         while( m-- ){
72             scanf( "%d", &op );
73             if( op == 1 ){
74                 scanf( "%d", &a );
75                 if( msum[1] < a ){
76                     puts( "0" ); continue;
77                 }
78                 int ans = query( a, 1, n, 1 );
79                 printf( "%d\n", ans );
80                 update( ans, ans + a - 1, 1, 1, n, 1 );
81             }
82             else{
83                 scanf( "%d %d", &a, &b );
84                 update( a, a + b - 1, 0, 1, n, 1 );
85             }
86         }
87     }
88     return 0;
89 }

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