Increasing Triplet Subsequence

Leetcode Problem 334: Increasing Triplet Subsequence

Problem Summary

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 exist, return false.

Techniques

• Track the smallest and second smallest elements
• Check for a third element greater than both

Solution

function increasingTriplet(nums: number[]): boolean {
    let currentI = Infinity
    let currentJ = Infinity

    for (let current = 0; current < nums.length; current++) {
        if (nums[current] <= currentI) {
            currentI = nums[current]
        } else if (nums[current] <= currentJ) {
            currentJ = nums[current]
        } else {
            return true
        }
    }

    return false
};

console.log([2,1,5,0,4,6])