Difficulty: Medium
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]given0 ≤ i < j < k ≤ n-1else 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.
Solutions:
double cursors (min + second min)