334. Increasing Triplet Subsequence

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Problem

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

Example 1:

Input: [1,2,3,4,5]
Output: true

Example 2:

Input: [5,4,3,2,1]
Output: false

Code

class Solution {
    public boolean increasingTriplet(int[] nums) {
        int min = Integer.MAX_VALUE;
        int secMin = Integer.MAX_VALUE;

        for(int num : nums) {
            if (num <= min) {
                min = num;
            } else if (num <= secMin) {
                secMin = num;
            } else if (num > secMin) {
                return true;
            }
        }

        return false;
    }
}