136 - Ugly Numbers

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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 replaced by the number computed.

Sample output

The 1500'th ugly number is <number>.

Solution

public class Main {

    public static void main (String[] args) {

        int size = 1500;

        int counter = 1;
        int result = 0;
        for (int i=2; counter<size; i++) {
            int x = i;

            while ((x%5==0)) {
                x/=5;
            };
            while ((x%3==0)) {
                x/=3;
            };
            while ((x%2==0)) {
                x/=2;
            };

            if (x==1) {
                counter++;
            }
            if (counter == size) result = i;
        }
        System.out.println("The 1500'th ugly number is " + result + ".");
        // The 1500'th ugly number is 859963392.
    }
}

關鍵字：UVa Online Judge, ACM. Java