丑数

#include <iostream>
#include <vector>
using namespace std;

//传统做法
bool  isUgly(int number)
{
    if(number%2==0)
         return isUgly(number/2);
    else if(number%3==0)
         return isUgly(number/3);
     else if(number%5==0)
          return isUgly(number/3);
     else
        return number==1?true:false;
}

//使用空间换取时间
int getNumber(int n)
{
    if(n<=1)
         return 0;
     int a=0,b=0,c=0;
     int i = 1;
     int *arr = new int[n];
     arr[0] = 1;
     while(i<n)
     {
         arr[i] = min(arr[a]*2,min(arr[b]*3,arr[c]*5));
         if(arr[i]==arr[a]*2)
                ++a;
         if(arr[i]==arr[b]*3)
              ++b;
         if(arr[i]==arr[c]*5)
               ++c;
         ++i;
     }
     return arr[i-1];
}

int findUgly(int n)
{
     if(n<=0)
        return 0;
     int number = 0;
     int uglyfound = 0;
     while(uglyfound<n)
     {
         ++number;
         if(isUgly(number))
             ++uglyfound;
     }
     return number;
}

int main()
{
    int n;
    while(cin>>n)
    {
        //cout<<findUgly(n)<<endl;
        cout<<getNumber(n)<<endl;
    }
    return 0;
}