CF #27E - Number With The Given Amount Of Divisors 已知因子个数求最小

#include<stdio.h>

typedef long long LL;
const LL INF = 1000000000000000010ll;
int p[12] = { 2,3,5,7,11,13,17,19,23,27,29,31};
int N;
void dfs( LL &ans, int i, LL x, int n ){
if( n > N ) return; // 基本减枝
if( n == N && ans > x ) ans = x;
for(int j = 1; j <= 60; j++){
if( ans/p[i] < x ) break;  // 若 ans < x*p[i] , 则当前p[i]的 j次不可能是最优.就没必要往后面枚举了.
dfs( ans, i+1, x*=p[i], n*(j+1) );
}
}
int main(){
while( scanf("%d",&N) != EOF){
LL ans = INF;
dfs( ans, 0, 1, 1 );
printf("%I64d\n", ans );
}
return 0;
}