(DP) poj 1338

Ugly Numbers

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

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<cstdlib>
#include<algorithm>
#include<queue>
#include<vector>
#include<stack>
using namespace std;
int n,ans[1505];
int main()
{
    ans[1]=1;
    int p1=1,p2=1,p3=1;
    for(int i=2;i<=1500;i++)
    {
        ans[i]=min(ans[p1]*2,min(ans[p2]*3,ans[p3]*5));
        if(ans[i]==ans[p1]*2) p1++;
        if(ans[i]==ans[p2]*3) p2++;
        if(ans[i]==ans[p3]*5) p3++;
    }
    while(scanf("%d",&n)!=EOF)
    {
        if(n==0)
            break;
        printf("%d\n",ans[n]);
    }
    return 0;
}