Skip to main content

Increasing Triplet Subsequence

Problem statement​

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: trueExplanation: Any triplet where i < j < k is valid.

Example 2:

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

Example 3:

Input: nums = [2,1,5,0,4,6]Output: trueExplanation: 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?

My solution​

/**
 * @param {number[]} nums
 * @return {boolean}
 */
var increasingTriplet = function(nums) {
    let first = Number.MAX_SAFE_INTEGER;
    let second = Number.MAX_SAFE_INTEGER;
    
    for (const num of nums) {
        if (num <= first) {
            first = num
        } else if (num <= second) {
            second = num
            // console.log(first, second)
        } else {
            return true
        }
    }
    
    // console.log(first, second)
    
    return false;
};