HDU1540 Tunnel Warfare 水题

分析：不需要线段树，set可过，STL大法好

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <set>
#include <stack>
using namespace std;
const int N=5e4+;
set<int>s;
bool d[N];
stack<int>p;
char o[];
int main()
{
    int n,m;
    while(~scanf("%d%d",&n,&m))
    {
        memset(d,,sizeof(d));
        while(!p.empty())p.pop();
        s.clear();
        while(m--)
        {
            int u;
            scanf("%s",o);
            if(o[]=='R')
            {
                u=p.top();
                p.pop();
                d[u]=;
                if(s.find(u)!=s.end())s.erase(u);
            }
            else if(o[]=='D')
            {
                scanf("%d",&u);
                d[u]=;
                if(s.find(u)==s.end())s.insert(u);
                p.push(u);
            }
            else
            {
                scanf("%d",&u);
                if(d[u])printf("0\n");
                else
                {
                    set<int>::iterator it=s.lower_bound(u);
                    int ans=n;
                    if(it!=s.end())ans=(*it)-;
                    ans=ans-u;
                    int x;
                    if(it==s.begin())x=;
                    else
                    {
                        it--;
                        x=(*it);
                    }
                    ans+=u-x;
                    printf("%d\n",ans);
                }
            }
        }
    }
}