Increasing Triplet Subsequence

题目地址：
https://leetcode.com/problems/increasing-triplet-subsequence/#/description

题目：

Given an unsorted array return whether an increasing subsequence of length 3 exists or not in the array.

Formally the function should:

Return true if there exists i, j, k 
such that arr[i] < arr[j] < arr[k] given 0 ≤ i < j < k ≤ n-1 else return false.

Your algorithm should run in O(n) time complexity and O(1) space complexity.

Examples:
Given [1, 2, 3, 4, 5],
return true.

Given [5, 4, 3, 2, 1],
return false.

解题思路：
start with two largest values, as soon as we find a number bigger than both, while both have been updated, return true.

代码：

public class IncreasingTripletSubsequence {

    public boolean increasingTriplet(int[] nums) {
        int small = Integer.MAX_VALUE, big = Integer.MAX_VALUE;
        for (int n : nums) {
            if (n <= small) { small = n; } // update small if n is smaller than both            else if (n <= big) { big = n; } // update big only if greater than small but smaller than big            else return true; // return if you find a number bigger than both        }
        return false;
    }

}