Super Ugly Number

Source

• leetcode: Super Ugly Number

Write a program to find the nth super ugly number.

Super ugly numbers are positive numbers whose all prime factors are in the given
prime list primes of size k. For example, [1, 2, 4, 7, 8, 13, 14, 16, 19,
26, 28, 32] is the sequence of the first
12 super ugly numbers given primes = [2, 7, 13, 19] of size 4.

Note:
(1) 1 is a super ugly number for any given primes.
(2) The given numbers in primes are in ascending order.
(3) 0 < k ≤ 100, 0 < n ≤ 106, 0 < primes[i] < 1000.

Java

public class Solution {
    public int nthSuperUglyNumber(int n, int[] primes) {
        int[] result = new int[n];
        result[0]=1;

        int[] index = new int[primes.length];

        for(int i=1; i<n; i++){
            result[i]=Integer.MAX_VALUE;
            for(int j=0; j<primes.length; j++){
                result[i] = Math.min(result[i], result[index[j]]*primes[j]);
            } 

            for(int j=0; j<primes.length; j++){
                if(result[i]/result[index[j]]==primes[j]) index[j]++;
            }
        }

        return result[n-1];
    }
}