HDU 1540 区间合并线段树

题目大意：

就是给定一堆位置，进行删除还原，最后找到 t 位置上的最大连续位置

 #include <cstdio>
 #include <cstring>
 #include <iostream>

 using namespace std;
 const int N = ;

 struct Node{
     int l , r , ml , mr , ma; //ml左最长，mr右最长，ma总最长
 }tree[N<<];

 void build(int o , int l , int r)
 {
     tree[o].l = l;
     tree[o].r = r;
     tree[o].ml = r - l + ;
     tree[o].mr = r - l + ;
     tree[o].ma = r - l + ;
     int m = (l + r) / ;
     if(l == r) return ;
     build(o<< , l , m);
     build(o<<| , m+ , r);
 }

 void push_up(int o)
 {
     int ls = o<< , rs = o<<|;
     tree[o].ml = tree[ls].ml;
     tree[o].mr = tree[rs].mr;

     if(tree[ls].ml == (tree[ls].r - tree[ls].l + ))
         tree[o].ml = tree[ls].ml + tree[rs].ml;

     if(tree[rs].mr == (tree[rs].r - tree[rs].l + ))
         tree[o].mr = tree[ls].mr + tree[rs].mr;

     tree[o].ma = max(tree[ls].mr + tree[rs].ml , tree[rs].ma);
     tree[o].ma = max(tree[ls].ma , tree[o].ma);
 }

 void update(int o , int t , int v)
 {
     if(tree[o].l == tree[o].r){
         if(v == ) tree[o].ma = tree[o].ml = tree[o].mr = ;
         else tree[o].ma = tree[o].ml = tree[o].mr = ;
         return ;
     }
     int ls = o<< , rs = o<<|;
     int m = (tree[o].l + tree[o].r) / ;

     if(t <= m) update(ls , t , v);
     else update(rs , t , v);
     //要等下层更新完才能递归回去更新上层
     push_up(o);
 }

 int query(int o , int t)
 {
     int ls = o<< , rs = o<<| , m = (tree[o].l + tree[o].r) / ;
     if(tree[o].l == tree[o].r || tree[o].ma ==  || tree[o].ma == tree[o].r - tree[o].l + )
         return tree[o].ma;

     if(t <= m){
         /*此时t属于左子树，那么存在t只属于左子树区间，和属于左右子树合并的区间
         ，弱属于合并的区间，那么要保证，t到左子树右端点形成的连续的个数要小于
         左子树最大右端连续和
         也就是 m - t + 1 <= tree[ls].mr (这里m也等于tree[ls].r)
         */
         if(t >= tree[ls].r - tree[ls].mr + )
             return query(ls , t) + query(rs , m+);
         else return query(ls , t);
     }else{
         if(t <= tree[rs].l + tree[rs].ml - )
             return query(ls , m) + query(rs , t);
         else query(rs , t);
     }
 }

 int que[N] , top;

 int main()
 {
  //   freopen("a.in" , "r" , stdin);
     int n,m;
     char str[];
     int x;
     while(scanf("%d%d",&n,&m)!=EOF){
         build(,,n);
         top=;
         while(m--)
         {
             scanf("%s",str);
             if(str[]=='D'){
                 scanf("%d",&x);
                 que[top++]=x;
                 update(,x,);
             }
             else if(str[]=='Q'){
                 scanf("%d",&x);
                 printf("%d\n",query(,x));
             }
             else{
                 if(x>){
                     x=que[--top];
                     update(,x,);
                 }
             }
         }
     }
     return ;
 }