334. Increasing Triplet Subsequence

class Solution {
    public boolean increasingTriplet(int[] nums) {
      int m1 = Integer.MAX_VALUE;
      int m2 = Integer.MAX_VALUE;
      
      for(int num : nums){
        if( m1 >= num){
          m1 = num;
        }else if(m2 >= num){
          m2 = num;
        }else{
          return true;
        }
      }
      return false;
    }
}

 

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