3105. Longest Strictly Increasing or Strictly Decreasing Subarray

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3105. Longest Strictly Increasing or Strictly Decreasing Subarray

Description

You are given an array of integers nums. Return the length of the longest subarray of nums which is either strictly increasing or strictly decreasing.

Example 1:

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Input: nums = [1,4,3,3,2]

Output: 2

Explanation:

The strictly increasing subarrays of `nums` are `[1]`, `[2]`, `[3]`, `[3]`, `[4]`, and `[1,4]`.

The strictly decreasing subarrays of `nums` are `[1]`, `[2]`, `[3]`, `[3]`, `[4]`, `[3,2]`, and `[4,3]`.

Hence, we return `2`.

Example 2:

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Input: nums = [3,3,3,3]

Output: 1

Explanation:

The strictly increasing subarrays of `nums` are `[3]`, `[3]`, `[3]`, and `[3]`.

The strictly decreasing subarrays of `nums` are `[3]`, `[3]`, `[3]`, and `[3]`.

Hence, we return `1`.

Example 3:

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Input: nums = [3,2,1]

Output: 3

Explanation:

The strictly increasing subarrays of `nums` are `[3]`, `[2]`, and `[1]`.

The strictly decreasing subarrays of `nums` are `[3]`, `[2]`, `[1]`, `[3,2]`, `[2,1]`, and `[3,2,1]`.

Hence, we return `3`.

Constraints:

  • 1 <= nums.length <= 50
  • 1 <= nums[i] <= 50

Hints/Notes

  • iterate the array twice

Solution

Language: C++

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class Solution {
public:
    int longestMonotonicSubarray(vector<int>& nums) {
        int res = 1;
        int curLen = 1;
        for (int i = 1; i < nums.size(); i++) {
            if (nums[i] > nums[i - 1]) {
                curLen += 1;
                res = max(res, curLen);
            } else {
                curLen = 1;
            }
        }
        curLen = 1;
        for (int i = 1; i < nums.size(); i++) {
            if (nums[i] < nums[i - 1]) {
                curLen += 1;
                res = max(res, curLen);
            } else {
                curLen = 1;
            }
        }
        return res;
    }
};