0334. Increasing Triplet Subsequence

https://leetcode.com/problems/increasing-triplet-subsequence

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?

ac

no topic, trick

class Solution {
    public boolean increasingTriplet(int[] nums) {
        int small = Integer.MAX_VALUE, big = Integer.MAX_VALUE;

        for (int n : nums) {
            if (n <= small) {
                small = n;
            } else if (n <= big) {
                big = n;
            } else {
                return true;
            }
        }

        return false;
    }
}