334. Increasing Triplet Subsequence

Given an integer array nums, return true if there exists a triple of indices (i, j, k) such that i < j < k and nums[i] < nums[j] < nums[k]. If no such indices exists, return false.

Example 1:

Input: nums = [1,2,3,4,5]
Output: true
Explanation: Any triplet where i < j < k is valid.

Example 2:

Input: nums = [5,4,3,2,1]
Output: false
Explanation: No triplet exists.

Example 3:

Input: nums = [2,1,5,0,4,6]
Output: true
Explanation: The triplet (3, 4, 5) is valid because nums[3] == 0 < nums[4] == 4 < nums[5] == 6.

def increasingTriplet(self, nums: List[int]) -> bool:
	if len(nums) < 3:
		return False

	first = float('inf')
	second = float('inf')

	for num in nums:
		if num <= first:
			first = num  # Update the smallest number
		elif num <= second:
			second = num  # Update the second smallest number
		else:
			# If we find a number greater than both, return True
			return True

	return False