Google Code Jam 2015 Round 1A Haircut 二分

题意：给你每个理发师的理发时间，问你排在队列中的第N个位置，问你应该被哪个理发师剪发。

解题思路：二分时间，看这个时间到第几个人理发了，然后找到临界值，看这个值的时候有那些理发师接待了新旅客的，即可找到那个理发师。

解题代码：

 1 // File Name: b.sample.cpp
 2 // Author: darkdream
 3 // Created Time: 2015年04月18日 星期六 09时05分30秒
 4
 5 #include<vector>
 6 #include<list>
 7 #include<map>
 8 #include<set>
 9 #include<deque>
10 #include<stack>
11 #include<bitset>
12 #include<algorithm>
13 #include<functional>
14 #include<numeric>
15 #include<utility>
16 #include<sstream>
17 #include<iostream>
18 #include<iomanip>
19 #include<cstdio>
20 #include<cmath>
21 #include<cstdlib>
22 #include<cstring>
23 #include<ctime>
24 #define LL long long
25
26 using namespace std;
27 LL a[1005];
28 LL b , n ;
29 LL count(LL t){
30     LL sum = 0 ;
31     for(int i = 1;i <= b;i ++)
32     {
33       sum += (t/a[i]) + 1 ;
34     }
35     return sum;
36 }
37 LL fen(LL l , LL  r){
38     LL m = (l + r)/2;
39     while(l<= r){
40         //printf("***\n");
41          m = (l + r)/2;
42          LL t = count(m);
43          if(t >= n){
44             r = m - 1;
45          }else l = m + 1;
46     }
47     return l ;
48 }
49 int main(){
50 //    freopen("B-large.in","r",stdin);
51 //    freopen("output","w",stdout);
52     LL T;
53     scanf("%lld",&T);
54     for(int ca = 1; ca <= T ;ca ++){
55         scanf("%lld %lld",&b,&n);
56         for(LL i = 1;i <= b;i ++)
57             scanf("%lld",&a[i]);
58         printf("Case #%d:",ca);
59         if(n <= b  )
60         {
61             printf(" %lld\n",n);
62             continue;
63         }
64         LL t = fen(1,1e15);
65         LL num = count(t-1);
66         for(int i = 1;i <= b;i ++){
67             if(t% a[i] == 0){
68                 num ++;
69             }
70             if(num == n)
71             {
72                 printf(" %d\n",i);
73                 break;
74             }
75         }
76
77     }
78
79 return 0;
80 }