原创 写出第1500个数（诺西笔试题）

/*

Ugly numbers are numbers whose only prime factors are 2,3or 5.
The sequence 1,2,3,4,5,6,8,9,10,12,15,…shows the first 11ugly numbers.
By convention,1 is included.
Write a time efficient program to find and print the 1500'th ugly number.(20 points)

*/

#include <stdio.h>

int cal_num(int seq);

int cal_num(int seq)
{

 int i,j;
 int cnt;
 int temp;
 cnt = 0;
 j = 0;
 
 while(1)
 {
  j++;
  i = j;
  if(i == 1)
  {
   cnt++;
   printf("%d:%d\n",cnt,j);
   if(cnt == seq)
   {
    return j;
   }
  }
  else
  {
   while(i % 2 == 0)
   {
    if(i /2 == 1 )
    {
     cnt++;
     printf("%d:%d\n",cnt,j);
     if(cnt  == seq)
     {
      return j;
     }
     else
     {
      break;
     }
     //i = 1;
    }
    else
    {
     i = i / 2;
    }
   }
   
   while((i % 3 == 0))
   {
    if(i / 3 == 1 )
    {
     cnt++;
     printf("%d:%d\n",cnt,j);
     if(cnt  == seq)
     {
      return j;
     }
     else
     {
      break;
     }
    }
    else
    {
     i = i / 3;
    }
   }

   while(i % 5 == 0)
   {
    if(i / 5 == 1 )
    {
     cnt++;
     printf("%d:%d\n",cnt,j);
     if(cnt  == seq)
     {
      return j;
     }
     else
     {
      break;
     }
    }
    else
    {
     i = i / 5;
    }
   }
   
  }//end else
  
 }
 return ;
}

int main(void)
{

 int num;
 num  = cal_num(1500);
 printf("num:%d\n",num);
 return 0;

}

此程序还可以进一步完善，哪些方面呢？

1.基本元素的个数，更加灵活，

2.输出第n个元素，也可以更加灵活

3封装函数与设计API