136 - Ugly Numbers

Ugly Numbers

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, 15, ...
shows the first 11 ugly numbers. By convention, 1 is included.
Write a program to find and print the 1500'th ugly number.

Input and Output

There is no input to this program. Output should consist of a single line as shown below, with <number> replaced by the number computed.

Sample output

The 1500'th ugly number is <number>.

Solution:
#include<stdio.h>
int main() {
   static int X, Y, Z, N;
   static long A[1501], x, y, z;
   A[1] = X = Y = Z = N = 1;
   while(N++ != 1500) {
       x = 2*A[X];
       y = 3*A[Y];
       z = 5*A[Z];

       if(x < y){
        if(x < z)
        A[N] = x;
       else
        A[N] = z;
       
       }else if(y < z)      
      A[N] = y;      
       else
        A[N] = z;
       if(A[N] == x) X++;
       if(A[N] == y) Y++;
       if(A[N] == z) Z++;
   }
   printf("The 1500'th ugly number is %ld.\n", A[1500]);
   return 0;
}