Ugly Numbers

Ugly Numbers
Time Limit: 1000MS Memory Limit: 10000K
Total Submissions: 21918 Accepted: 9788

Description
Ugly numbers are numbers whose only prime factors are 2, 3 or 5. The sequence
1, 2, 3, 4, 5, 6, 8, 9, 10, 12, …
shows the first 10 ugly numbers. By convention, 1 is included.
Given the integer n,write a program to find and print the n’th ugly number.

Input
Each line of the input contains a postisive integer n (n <= 1500).Input is terminated by a line with n=0.

Output
For each line, output the n’th ugly number .:Don’t deal with the line with n=0.

Sample Input

1
2
9
0

Sample Output

1
2
10

Source
New Zealand 1990 Division I,UVA 136
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#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#define LL long long
using namespace std;

const LL MAX = 1e15;

LL a[15500];
int main()
{
    LL b,c,d;
    int top=0;
    //freopen("output.txt","w",stdout);
    for(int i=0;i<=30;i++)
    {
        if(i==0)
        {
            b=1;
        }
        else
        {
            b*=2;
        }
        if(b>MAX)
        {
            break;
        }
        for(int j=0;j<=30;j++)
        {
            if(j==0)
            {
                c=1;

            }
            else
            {
                c*=3;
            }
            if(b*c>MAX)
            {
                break;
            }
            for(int k=0;k<=30;k++)
            {
                if(k==0)
                {
                    d=1;
                }
                else
                {
                    d*=5;
                }
                if(b*c*d>MAX)
                {
                    break;
                }
                a[top++]=b*c*d;
                //printf("%lld\n",b*c*d);
            }
        }
    }
    sort(a,a+top);
    int n;
    while(scanf("%d",&n)&&n)
    {
        printf("%lld\n",a[n-1]);
    }
    return 0;
}