334. Increasing Triplet Subsequence

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.

Solution：Round1

思路： Simple count and check
Time Complexity: O(N) Space Complexity: O(1)

Solution Code：

class Solution {
    public boolean increasingTriplet(int[] nums) {
    
        int a = Integer.MAX_VALUE, b = Integer.MAX_VALUE;
        for(int i = 0; i < nums.length; i++) {
            if(nums[i] > b) {
                return true;
            }
            else if(nums[i] > a) {
                b = nums[i];
            }
            else {
                a = nums[i];
            }
        }
        return false;
    }
}