poj3667---Hotel 线段树区间合并，区间更新

题意：有N个房间，M次操作。有两种操作（1）"1 a"，表示找到连续的长度为a的空房间，如果有多解，优先左边的，即表示入住。（2）"2 b len"，把起点为b长度的len的房间清空，即退房。三个数组分别记录   lsum区间左值       rsum区间右值       sum区间最大值。

 #include <set>
 #include <map>
 #include <cmath>
 #include <ctime>
 #include <queue>
 #include <stack>
 #include <cctype>
 #include <cstdio>
 #include <string>
 #include <vector>
 #include <cstdlib>
 #include <cstring>
 #include <iostream>
 #include <algorithm>
 using namespace std;
 typedef unsigned long long ull;
 typedef long long ll;
 const int inf = 0x3f3f3f3f;
 const double eps = 1e-;
 template <class T>
 inline bool scan_d(T &ret)
 {
     char c;
     int sgn;
     if(c=getchar(),c==EOF) return ;
     while(c!='-'&&(c<''||c>'')) c=getchar();
     sgn=(c=='-')?-:;
     ret=(c=='-')?:(c-'');
     while(c=getchar(),c>=''&&c<='') ret=ret*+(c-'');
     ret*=sgn;
     return ;
 }

 const int maxn = 5e4+;
 int lv[maxn<<],rv[maxn<<], setv[maxn<<];          //lv，rv数组可有可无，lsum rsum数组已经包含了他们的意义。
 int lsum[maxn<<],rsum[maxn<<],sum[maxn<<];

 void push_up(int l,int r,int pos)
 {
     lv[pos] = lv[pos<<];
     rv[pos] = rv[pos<<|];
     lsum[pos] = lsum[pos<<];
     rsum[pos] = rsum[pos<<|];
     sum[pos] = max(sum[pos<<],sum[pos<<|]);
     sum[pos] = max(sum[pos],rsum[pos<<]+lsum[pos<<|]);
     int mid = (l + r) >> ;
     if (rv[pos<<] ==lv[pos<<|] && !rv[pos<<])
     {
         if (lsum[pos<<] == mid - l + )
             lsum[pos] += lsum[pos<<|];
         if (rsum[pos<<|] == r - mid)
             rsum[pos] += rsum[pos<<];
         sum[pos] = max(sum[pos],rsum[pos<<]+lsum[pos<<|]);
     }
 }

 void push_down(int l,int r,int pos)
 {
     if (~setv[pos])
     {
         int mid = (l + r) >> ;
         setv[pos<<] = setv[pos<<|] = setv[pos];
         lv[pos<<] = setv[pos];
         lv[pos<<|] = setv[pos];
         rv[pos<<] = setv[pos];
         rv[pos<<|] = setv[pos];
         lsum[pos<<] = (setv[pos] ?  : (mid-l+));
         rsum[pos<<] = (setv[pos] ?  : (mid-l+));
         lsum[pos<<|] = (setv[pos] ?  : (r-mid));
         rsum[pos<<|] = (setv[pos] ?  : (r-mid));
         sum[pos<<] = (setv[pos] ?  : (mid-l+));
         sum[pos<<|] = (setv[pos] ?  : (r-mid));
         setv[pos] = -;
     }
 }

 void build (int l,int r,int pos)
 {
     if (l == r)
     {
         rv[pos] = lv[pos] = ;
         sum[pos] = lsum[pos] = rsum[pos] = ;
         return;
     }
     int mid = (l + r) >> ;
     build(l,mid,pos<<);
     build(mid+,r,pos<<|);
     push_up(l,r,pos);
 }

 void update(int l,int r,int pos,int ua,int ub,int val)
 {
     if (ua <= l && ub >= r)
     {
         setv[pos] = val;
         lv[pos] = val;
         rv[pos] = val;
         lsum[pos] = (val ?  : (r-l+));
         rsum[pos] = (val ?  : (r-l+));
         sum[pos] =  (val ?  : (r-l+));
         return;
     }
     int mid = (l + r) >> ;
     push_down(l,r,pos);
     if (ua <= mid)
         update(l,mid,pos<<,ua,ub,val);
     if (ub > mid)
         update(mid+,r,pos<<|,ua,ub,val);
     push_up(l,r,pos);
 }

 int query(int l,int r,int pos,int x)
 {
     if (lsum[pos] >= x)
     {
         return l;

     }
     int mid = (l + r) >> ;
     push_down(l,r,pos);
     if (sum[pos<<] >= x)
          return query(l,mid,pos<<,x);
     /*else if (rsum[pos<<1]&&rsum[pos<<1] + lsum[pos<<1|1] >= x)          //注释部分是错误的，，看起来很像但是不一样的
         return query(l,mid,pos<<1,rsum[pos<<1]);*/
     else if (rsum[pos<<] + lsum[pos<<|] >= x)
         return mid+-rsum[pos<<];
     else
         return query(mid+,r,pos<<|,x);
 }

 int main(void)
 {
     #ifndef ONLINE_JUDGE
     freopen("in.txt","r",stdin);
     #endif
     int n,q;
     while (~scanf ("%d%d",&n,&q))
     {
         build(,n,);
         memset(setv,-,sizeof(setv));
         for (int i = ; i < q; i++)
         {
             int op,x,y;
             scanf ("%d",&op);
             if (op == )
             {
                 scanf ("%d",&x);
                 if (sum[] < x)
                 {
                     printf("0\n");
                     continue;
                 }
                 int p = query(,n,,x);
                 printf("%d\n",p);
                 update(,n,,p,p+x-,);
             }
             else
             {
                 scanf ("%d%d",&x,&y);
                 update(,n,,x,y+x-,);
             }
         }
     }
     return ;
 }