Description
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.
Constraints:
1 <= nums.length <= 5 * 105-231 <= nums[i] <= 231 - 1
Follow up: Could you implement a solution that runs in
O(n) time complexity and O(1) space complexity?
Solution
Python3
class Solution:
def increasingTriplet(self, nums: List[int]) -> bool:
first = second = inf
for num in nums:
if num < first:
first = num
elif num > first and num < second:
second = num
elif num > second:
return True
return False