bzoj1225

Posted 2020-10-17 宣毅鸣

题解：

数论+报搜

首先套一个计算因子个数的公式

枚举一下这个数

代码：

#include<bits/stdc++.h> 
using namespace std;  
int n,ans[100005],res[21],tmp[21];
int pri[]={0,2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53};  
double mn=DBL_MAX,lg[21];  
void dfs(double x,int y,int z)
{  
    if (x>=mn)return;  
    if (y==1)  
     {  
        mn=x;  
        memset(res,0,sizeof(res));  
        for(int i=1;i<=z-1;i++)res[i]=tmp[i];  
        return;  
     }  
    if (z>16)return;  
    for (int i=0;(i+1)*(i+1)<=y;i++)
     if (y%(i+1)==0)  
      {  
        if (i!=0)  
         {  
            tmp[z]=i;  
            dfs(x+lg[z]*i,y/(i+1),z+1);  
         }  
        if ((i+1)*(i+1)!=y)  
         {  
            tmp[z]=y/(i+1)-1;  
            dfs(x+lg[z]*(y/(i+1)-1),i+1,z+1);  
         }  
      }  
}  
int main()  
{  
    scanf("%d",&n);  
    for (int i=1;i<=16;i++)lg[i]=log(pri[i]);  
    dfs(0,n,1);  
    ans[0]=ans[1]=1;  
    for (int i=1;i<=16;i++)   
     for (;res[i]>0;res[i]--)  
      {  
        for (int j=1;j<=ans[0];j++)ans[j]*=pri[i];  
        for (int j=1;j<=ans[0];j++)ans[j+1]+=ans[j]/10,ans[j]%=10;  
        if (ans[ans[0]+1]!=0)  ans[0]++;  
        while (ans[ans[0]]/10!=0)  
         ans[ans[0]+1]+=ans[ans[0]]/10,ans[ans[0]]%=10,++ans[0];  
      }  
    for (int i=ans[0];i>=1;i--)printf("%d",ans[i]);    
    return 0;  
}