codeforces 27E . Number With The Given Amount Of Divisors 搜索+数论

#include <iostream>
#include <vector>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <map>
#include <set>
#include <string>
#include <queue>
#include <stack>
#include <bitset>
using namespace std;
#define pb(x) push_back(x)
#define ll long long
#define mk(x, y) make_pair(x, y)
#define lson l, m, rt<<1
#define mem(a) memset(a, 0, sizeof(a))
#define rson m+1, r, rt<<1|1
#define mem1(a) memset(a, -1, sizeof(a))
#define mem2(a) memset(a, 0x3f, sizeof(a))
#define rep(i, n, a) for(int i = a; i<n; i++)
#define fi first
#define se second
typedef pair<int, int> pll;
const double PI = acos(-1.0);
const double eps = 1e-8;
const int mod = 1e9+7;
const int inf = 1061109567;
const int dir[][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1} };
int n, f[105], prime[20], cnt;
ll ans = 1e18+2;
void dfs(int pos, int num, ll val) {
if(pos>16)
return ;
if(num>n)
return ;
if(num == n) {
ans = min(ans, val);
return ;
}
for(int i = 1; i<=60; i++) {
val *= prime[pos];
if(val>ans)
break;
dfs(pos+1, num*(i+1), val);
}
}
int main()
{
cin>>n;
for(int i = 2; i<100; i++) {
if(!f[i]) {
for(int j = i+i; j<100; j+=i) {
f[j] = 1;
}
prime[cnt++] = i;
}
}
dfs(0, 1, 1);
cout<<ans<<endl;
return 0;
}