codeforce E. Number With The Given Amount Of Divisor

Topic link address: http://codeforces.com/problemset/problem/27/E

Question: Given a number , find the smallest positive integer such that the number of factors is .

Analysis: Similar to the method for finding factors, first build a search tree, build a tree structure with each one as a layer, perform a search, and take the smallest one.

 

Taking an example to illustrate, the construction is as follows: 

 

It can be seen that all numbers on the path from the root node to each leaf node are multiplied by the divisor of 12, so 12 has 6 divisors.

The idea of ​​​​searching is obvious. From the root node to perform a deep search, to the leaf node, the code is as follows:

    void dfs(int dept,LL ans = 1)  
    {  
        if(dept == cnt)  
        {  
            make[ct ++] = ans;  
            return ;  
        }  
        for(int i=0;i<=num[dept];i++)  
        {  
            dfs(dept + 1 , years);  
            years *= pri[dept];  
        }  
    }