POJ 2892 Tunnel Warfare(树状数组+二分)

题目链接

二分求上界和下界，树状数组。注意特殊情况。

 #include <cstring>
 #include <cstdio>
 #include <string>
 #include <iostream>
 #include <algorithm>
 #include <vector>
 using namespace std;
 int p[];
 int o[];
 int stack[];
 int n;
 int lowbit(int t)
 {
     return t&(-t);
 }
 void insert(int t,int d)
 {
     while(t <= n)
     {
         p[t] += d;
         t += lowbit(t);
     }
 }
 int getsum(int t)
 {
     int sum = ;
     while(t > )
     {
         sum += p[t];
         t -= lowbit(t);
     }
     return sum;
 }
 int fr(int x)
 {
     int str,end,temp,mid;
     str = ;
     end = n;
     while(str < end)
     {
         mid = (str+end+)/;
         temp = getsum(mid);
         if(temp > x)
             end = mid-;
         else
             str = mid;
     }
     return end;
 }
 int fl(int x)
 {
     int str,end,temp,mid;
     str = ;
     end = n;
     while(str < end)
     {
         mid = (str+end)/;
         temp = getsum(mid);
         if(temp < x)
             str = mid+;
         else
             end = mid;
     }
     return str;
 }
 int main()
 {
     int i,m,top,num,t;
     char ch[];
     while(scanf("%d%d",&n,&m)!=EOF)
     {
         top = ;
         for(i = ;i <= n;i ++)
         {
             p[i] = ;
             o[i] = ;
         }
         for(i = ; i <= m; i ++)
         {
             scanf("%s",ch);
             if(ch[] == 'R')
             {
                 if(top != )
                 {
                     o[stack[top]] = ;
                     insert(stack[top--],-);
                 }
             }
             else if(ch[] == 'D')
             {
                 scanf("%d",&num);
                 stack[++top] = num;
                 if(o[num] == )
                 {
                     o[num] = ;
                     insert(num,);
                 }
             }
             else if(ch[] == 'Q')
             {
                 scanf("%d",&num);
                 if(o[num])
                     printf("0\n");
                 else
                 {
                     t = getsum(num);
                     if(t == )//注意一下
                     printf("%d\n",fr(t));
                     else
                     printf("%d\n",fr(t)-fl(t));
                 }
             }
         }
     }
     return ;
 }