leetcode 264. Ugly Number II

Seawolf

Write a program to find the n-th ugly number.

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. 

Example:

Input: n = 10
Output: 12
Explanation: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugly numbers.
Note:  

1 is typically treated as an ugly number.
n does not exceed 1690.

class Solution {
    public int nthUglyNumber(int n) {
        int[] arr = new int[n+1];
        int t2 = 1, t3 = 1, t5 = 1;
        arr[1] = 1;
        for(int i = 2 ; i <= n ; i++){
            arr[i] = Math.min (Math.min(2*arr[t2], 3*arr[t3]),5*arr[t5]);
            
            if(arr[i] == 2*arr[t2]) t2++;
            if(arr[i] == 3*arr[t3]) t3++;
            if(arr[i] == 5*arr[t5]) t5++;
        }
        
        return arr[n];
        
    }
    
}