[Leetcode 264] Ugly Number II

标签：leetcode   math   

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

Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugly numbers.

Note that 1 is typically treated as an ugly number.

1. An ugly number must be multiplied by either 2, 3, or 5 from a smaller ugly number.

public int nthUglyNumber(int n) {
        SortedSet<Long> s1 = new TreeSet<>();
        s1.add((long)1);
        long result = s1.first();
        for(int i=0;i<n;i++){
            result = s1.first();
            s1.add(result * 2);
            s1.add(result * 3);
            s1.add(result * 5);
            s1.remove(result);
        }
        return (int)result;
    }

[Leetcode 264] Ugly Number II

标签：leetcode   math   

原文地址：http://blog.csdn.net/sbitswc/article/details/48168159