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。

  1 #include <cstring>

  2 #include <cstdio>

  3 #include <string>

  4 #include <iostream>

  5 #include <algorithm>

  6 #include <vector>

  7 using namespace std;

  8 int p[100001];

  9 int o[100001];

 10 int stack[100001];

 11 int n;

 12 int lowbit(int t)

 13 {

 14     return t&(-t);

 15 }

 16 void insert(int t,int d)

 17 {

 18     while(t <= n)

 19     {

 20         p[t] += d;

 21         t += lowbit(t);

 22     }

 23 }

 24 int getsum(int t)

 25 {

 26     int sum = 0;

 27     while(t > 0)

 28     {

 29         sum += p[t];

 30         t -= lowbit(t);

 31     }

 32     return sum;

 33 }

 34 int fr(int x)

 35 {

 36     int str,end,temp,mid;

 37     str = 1;

 38     end = n;

 39     while(str < end)

 40     {

 41         mid = (str+end+1)/2;

 42         temp = getsum(mid);

 43         if(temp > x)

 44             end = mid-1;

 45         else

 46             str = mid;

 47     }

 48     return end;

 49 }

 50 int fl(int x)

 51 {

 52     int str,end,temp,mid;

 53     str = 1;

 54     end = n;

 55     while(str < end)

 56     {

 57         mid = (str+end)/2;

 58         temp = getsum(mid);

 59         if(temp < x)

 60             str = mid+1;

 61         else

 62             end = mid;

 63     }

 64     return str;

 65 }

 66 int main()

 67 {

 68     int i,m,top,num,t;

 69     char ch[12];

 70     while(scanf("%d%d",&n,&m)!=EOF)

 71     {

 72         top = 0;

 73         for(i = 1;i <= n;i ++)

 74         {

 75             p[i] = 0;

 76             o[i] = 0;

 77         }

 78         for(i = 1; i <= m; i ++)

 79         {

 80             scanf("%s",ch);

 81             if(ch[0] == 'R')

 82             {

 83                 if(top != 0)

 84                 {

 85                     o[stack[top]] = 0;

 86                     insert(stack[top--],-1);

 87                 }

 88             }

 89             else if(ch[0] == 'D')

 90             {

 91                 scanf("%d",&num);

 92                 stack[++top] = num;

 93                 if(o[num] == 0)

 94                 {

 95                     o[num] = 1;

 96                     insert(num,1);

 97                 }

 98             }

 99             else if(ch[0] == 'Q')

100             {

101                 scanf("%d",&num);

102                 if(o[num])

103                     printf("0\n");

104                 else

105                 {

106                     t = getsum(num);

107                     if(t == 0)//注意一下

108                     printf("%d\n",fr(t));

109                     else

110                     printf("%d\n",fr(t)-fl(t));

111                 }

112             }

113         }

114     }

115     return 0;

116 }