Algorithm
LeetCode 75
Increasing Triplet Subsequence

334. Increasing Triplet Subsequence

Tags

  • Array
  • Greedy

Link

https://leetcode.com/problems/increasing-triplet-subsequence/description/?envType=study-plan-v2&envId=leetcode-75 (opens in a new tab)

Question

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?

Answer

JavaScript

/**
 * @param {number[]} nums
 * @return {boolean}
 */
var increasingTriplet = function (nums) {
  let first = Number.MAX_SAFE_INTEGER,
    second = Number.MAX_SAFE_INTEGER;
  for (let i = 0; i < nums.length; i++) {
    if (nums[i] <= first) {
      first = nums[i];
    } else if (nums[i] <= second) {
      second = nums[i];
    } else {
      return true;
    }
  }
  return false;
};
/**
 * @param {number[]} nums
 * @return {boolean}
 */
var increasingTriplet = function (nums) {
  let first = Infinity,
    second = Infinity;
  for (const num of nums) {
    if (num <= first) {
      first = num;
    } else if (num > first && num <= second) {
      second = num;
    } else if (num > first && num > second) {
      return true;
    }
  }
  return false;
};
Greatest Common Divisor of StringsIs Subsequence