1. Problem
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.
Constraints:
- 1 <= nums.length <= 5 * 10^5
- -2^31 <= nums[i] <= 2^31 - 1
2. Solution
I solved this problem like this.
2.1. Time problem code
This code is simple logic. We just check using for statement. But, it makes Time Limit Exceeded problem.
class Solution:
def increasingTriplet(self, nums: List[int]) -> bool:
for i in range(len(nums)):
for j in range(i+1, len(nums)):
if nums[i] >= nums[j]:
continue
for k in range(j+1, len(nums)):
if nums[j] < nums[k]:
return True
return False
2.2. Solution
Other solution is like this. This solution is simple and easy to understand.
class Solution:
def increasingTriplet(self, nums: List[int]) -> bool:
first = second = float('inf')
for n in nums:
if n <= first:
first = n
elif n <= second:
second = n
else:
return True
return False