【朱迪的LeetCode刷题笔记】】334. Increasing Triplet Subsequence #Medium #Python

Judie

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?

Judy
Python taught by Mike

class Solution(object):
    def increasingTriplet(self, nums):
        """
        :type nums: List[int]
        :rtype: bool
        """
        i = None
        j = None
        for n in nums:
            if i == None or n < i:
                i = n 
            elif j == None:
                if n > i:
                    j = n   
                else:
                    continue 
            elif n > j:
                return True   
            elif i < n < j:
                j = n
        return False

Sol1
Python
https://leetcode.com/problems/in ... p;envId=leetcode-75

def increasingTriplet(nums):
    first = second = float('inf')
    for n in nums:
        if n <= first:
            first = n
        elif n <= second:
            second = n
        else:
            return True
    return False

sfqxx