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.

#include<iostream>
using namespace std;
long long heap[5000000];
long long ualy[2000];
void swap(long long  &a,long long &b);
void put(int &len,long long num);
long long get(int &len);
int main()
{
   
 heap[1]=1;
 int len=1;
 long long n,num,pre=0;
 int i;
 for(i=1;i<=1500;)
 {
  num=get(len);
  if(pre!=num)
  {
   ualy[i++]=num;
   pre=num;
   put(len,2*num);
   put(len,3*num);
   put(len,5*num);
  }
 }
 while(cin>>n&&n)
 {
  cout<<ualy[n]<<endl;
 }
 return 0;
}
void swap(long long &a,long long &b)
{
 long long temp;
 temp=a;
 a=b;
 b=temp;
}
void put(int &len,long long num)
{
 len++;
 heap[len]=num;
 int son=len;
 while(son!=1&&heap[son]<heap[son/2])
 {
  swap(heap[son],heap[son/2]);
  son/=2;
 }
}
long long get(int &len)
{
 long long min=heap[1];
 heap[1]=heap[len];
 --len;
 int son=1;
 while(son*2<=len)
 {
  if(son*2+1>len||heap[son*2]<heap[son*2+1])
   son=son*2;
  else
   son=son*2+1;
  if(heap[son/2]>heap[son])
   swap(heap[son],heap[son/2]);
  else
   break;
 }
 return min;
}