Calling Extraterrestrial Intelligence Again

http://162.105.81.212/JudgeOnline/problem?id=1411

本来以为很容易就过了的，以前在杭电做过，可没想到超时了；

后来剪了n次枝，提交了4,5次终于过了，以后在一个OJ上过了，再拿到其它OJ上试试，有可能会WA或TLE(尤其是搜索类题目)；

这题比较有纪念意义，是第一道通过自己剪枝从ＴＬＥ到ＡＣ的.

#include <stdio.h>int prime[1230] , n , m , a , b ;void PrimeList ()//素数表{int i , j , g ;prime[0] = 2 , prime[1] = 3 , prime[2] = 5 ;for (n = 3 , i = 7 , g = 4 ; i < 10000 ; i += g , g = 6 - g){for (j = 0 ; prime[j] * prime[j] <= i ; j ++)if (i % prime[j] == 0)break ;if (prime[j] * prime[j] > i)prime[n ++] = i ;}}int Bsearch (int key){int low , high , mid ;low = 0 ;high = n - 1 ;while (low <= high){mid = (low + high) >> 1 ;if (key == prime[mid])return mid ;else if (key < prime[mid])high = mid - 1 ;elselow = mid + 1 ;}return high ;}void Comp (){int i , j , p , q , ans ;ans = 0 , i = n - 1 ;while (prime[i] * 2 > m)i -- ;for ( ; i >= 0 ; i --){if (prime[i] * prime[i] <= ans)break ;j = Bsearch (m / prime[i]) ;//二分查找上限,加上这个优化之后就过了if (j > i)//分子要不大于分母j = i ;for ( ; j >= 0 && prime[i] * prime[j] > ans ; j --){if (b * prime[j] < a * prime[i])break ;if (prime[i] * prime[j] <= m){p = prime[j] ;q = prime[i] ;ans = p * q ;}}}printf ("%d %d/n" , p , q) ;}int main (){PrimeList () ;while (scanf ("%d%d%d" , &m , &a , &b) , m , a , b)Comp () ;return 0 ;}