Today I have done leetcode's October LeetCoding Challenge with cpp.

October LeetCoding Challenge 11

Description

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

Follow up: Could you implement a solution that runs in O(n) time complexity and O(1) space complexity?

Solution

class Solution {
public:
  bool increasingTriplet(vector<int>& nums) {
    int min = INT_MAX, middle = INT_MAX;
    for(auto i : nums) {
      if(i < min) {
        min = i;
      } else if (i > min && i < middle) {
        middle = i;
      } else if (i > middle) {
        return true;
      }
    }
    return false;
  }
};

// Accepted
// 76/76 cases passed (79 ms)
// Your runtime beats 88.38 % of cpp submissions
// Your memory usage beats 67.34 % of cpp submissions (61.6 MB)