[LeetCode] Longest Continuous Increasing Subsequence

Problem: Given an unsorted array of integers nums, return the length of the longest continuous increasing subsequence (i.e. subarray). The subsequence must be strictly increasing.

A continuous increasing subsequence is defined by two indices l and r (l < r) such that it is [nums[l], nums[l + 1], ..., nums[r - 1], nums[r]] and for each l <= i < r, nums[i] < nums[i + 1].

Example:

Input: nums = [1,3,5,4,7]
Output: 3
Explanation: The longest continuous increasing subsequence is [1,3,5] with length 3.
Even though [1,3,5,7] is an increasing subsequence, it is not continuous as elements 5 and 7 are separated by element 4.

Input: nums = [2,2,2,2,2]
Output: 1
Explanation: The longest continuous increasing subsequence is [2] with length 1. Note that it must be strictly increasing.

Approach: It's a simple implementation problem. You can directly look at the implementation to understand the approach.

Implementation in C#:

    public int FindLengthOfLCIS(int[] nums)

    {

        int length = nums?.Length ?? 0;

        if (length <= 1)

        {

            return length;

        }

        int maxCISLength = 1;

        int currCISLength = 1;

        int prevIndex = 0;

        for (int i = 1; i < length; ++i)

        {

            if (nums[i] > nums[prevIndex])

            {

                ++currCISLength;

                if (currCISLength > maxCISLength)

                {

                    maxCISLength = currCISLength;

                }

            }

            else

            {

                currCISLength = 1;

            }

            prevIndex = i;

        }

        return maxCISLength;

    }

Complexity: O(n)