hdu 1540 Tunnel Warfare（单点更新，取最大连续区间）★

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <cstring>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <map>
using namespace std;
#define INF 0x3f3f3f3f
#define maxn 50010
stack <int> s;
struct node
{
int left,right;
int ls,rs,ms;
}tree[maxn<<2];

void build(int l,int r,int pos)
{
tree[pos].left = l;
tree[pos].right = r;
tree[pos].ls = tree[pos].rs = tree[pos].ms = r-l+1;
if(l == r)
return;
int mid = (l+r)>>1;
build(l,mid,pos<<1);
build(mid+1,r,pos<<1|1);
}
void update(int pos,int k,int state)
{
if(tree[pos].left == tree[pos].right)
{
tree[pos].ls = tree[pos].rs = tree[pos].ms = state;
return;
}
int mid = (tree[pos].left+tree[pos].right)>>1;
if(k<=mid)
update(pos<<1,k,state);
else
update(pos<<1|1,k,state);
tree[pos].ls = tree[pos<<1].ls;
tree[pos].rs = tree[pos<<1|1].rs;
tree[pos].ms = max(max(tree[pos<<1].ms,tree[pos<<1|1].ms),tree[pos<<1].rs+tree[pos<<1|1].ls);
if(tree[pos<<1].ls == tree[pos<<1].right-tree[pos<<1].left+1)
tree[pos].ls += tree[pos<<1|1].ls;
if(tree[pos<<1|1].rs == tree[pos<<1|1].right-tree[pos<<1|1].left+1)
tree[pos].rs += tree[pos<<1].rs;
}

int query(int pos,int k)
{
if(tree[pos].ms==0 || tree[pos].ms==tree[pos].right-tree[pos].left+1 || tree[pos].left==tree[pos].right)
return tree[pos].ms;
int mid = (tree[pos].left+tree[pos].right)>>1;
if(k <= tree[pos<<1|1].left+tree[pos<<1|1].ls-1 && k >= tree[pos<<1].right-tree[pos<<1].rs+1)
return tree[pos<<1].rs+tree[pos<<1|1].ls;
else if(k <= mid)
return query(pos<<1,k);
else if(k > mid)
return query(pos<<1|1,k);/*
if(k<=mid)
{
if(k>=tree[pos<<1].right-tree[pos<<1].rs+1)
return query(pos<<1,k)+query(pos<<1|1,mid+1);
else
return query(pos<<1,k);
}
else
{
if(k<=tree[pos<<1|1].left+tree[pos<<1|1].ls-1)
return query(pos<<1|1,k)+query(pos<<1,mid);
else
return query(pos<<1|1,k);
}*/
}

int main()
{
int n,m;
while(scanf("%d%d",&n,&m)!=EOF)
{
build(1,n,1);
s.empty();
char c;
int x;
for(int i = 0; i < m; i++)
{
getchar();
scanf("%c",&c);
if(c == 'D')
{
scanf("%d",&x);
update(1,x,0);
s.push(x);
}
else if(c == 'Q')
{
scanf("%d",&x);
printf("%d\n",query(1,x));
}
else
{
update(1,s.top(),1);
s.pop();
}
}
}
return 0;
}