increasing-triplet-subsequence

Definition

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

Input: An array Output: True or False

Formal Definition of the function

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

Examples

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

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

Example 3: Input: [5, 3, 1, 6, 3, 8] Output: true

Gotchas

• Need to set the second_min to the highest number in the language, or else it might conflict with the min pointer.

Questions to ask

• Should the numbers need to be able to be increased consecutively. Or if ANY three numbers are in increasing order do they count?

Things learned

• It is important in this question to specify exactly what the question is asking for. It seems that it could be extremely simple, deceptively simple, and would throw many people off track with an unclear definition.