CodeForces - 27E

https://vjudge.net/problem/CodeForces-27E

求因子个数为n的最小的数
dfs枚举质因子的幂

#include <iostream>
#include <cstdio>
#include <queue>
#include <algorithm>
#include <cmath>
#include <cstring>
#define inf ~0
#define N 1000010
#define p(a) putchar(a)
#define For(i,a,b) for(unsigned long long i=a;i<=b;++i)

using namespace std;
unsigned long long n,ans;
unsigned long long prime[]={,,,,,,,,,,,,,,,};
void in(unsigned long long &x){
    unsigned long long y=;char c=getchar();x=;
    while(c<''||c>''){if(c=='-')y=-;c=getchar();}
    while(c<=''&&c>=''){ x=(x<<)+(x<<)+c-'';c=getchar();}
    x*=y;
}
void o(unsigned long long x){
    if(x<){p('-');x=-x;}
    if(x>)o(x/);
    p(x%+'');
}

void dfs(unsigned long long depth,unsigned long long num,unsigned long long cnt,unsigned long long up){
    if(cnt>n)
        return;
    if(cnt==n&&ans>num){
        ans=num;
        return;
    }
    For(i,,up){
        if(num*prime[depth]>ans) return;
        dfs(depth+,num*=prime[depth],cnt*(i+),i);
    }
}

int main(){
    in(n);
    ans=inf;
    dfs(,,,);
    o(ans);
    return ;
}