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978. Longest Turbulent Subarray

Description

Given an integer array arr, return the length of a maximum size turbulent subarray of arr.

A subarray is turbulent if the comparison sign flips between each adjacent pair of elements in the subarray.

More formally, a subarray [arr[i], arr[i + 1], ..., arr[j]] of arr is said to be turbulent if and only if:

• For i <= k < j:
  • arr[k] > arr[k + 1] when k is odd, and
  • arr[k] < arr[k + 1] when k is even.
• Or, for i <= k < j:
  • arr[k] > arr[k + 1] when k is even, and
  • arr[k] < arr[k + 1] when k is odd.

 

Example 1:

Input: arr = [9,4,2,10,7,8,8,1,9]
Output: 5
Explanation: arr[1] > arr[2] < arr[3] > arr[4] < arr[5]

Example 2:

Input: arr = [4,8,12,16]
Output: 2

Example 3:

Input: arr = [100]
Output: 1

 

Constraints:

• 1 <= arr.length <= 4 * 104
• 0 <= arr[i] <= 109

Solutions

• Java
• C++
• Python
• Go
• TypeScript

• class Solution {
      public int maxTurbulenceSize(int[] arr) {
          int ans = 1, f = 1, g = 1;
          for (int i = 1; i < arr.length; ++i) {
              int ff = arr[i - 1] < arr[i] ? g + 1 : 1;
              int gg = arr[i - 1] > arr[i] ? f + 1 : 1;
              f = ff;
              g = gg;
              ans = Math.max(ans, Math.max(f, g));
          }
          return ans;
      }
  }
  

• class Solution {
  public:
      int maxTurbulenceSize(vector<int>& arr) {
          int ans = 1, f = 1, g = 1;
          for (int i = 1; i < arr.size(); ++i) {
              int ff = arr[i - 1] < arr[i] ? g + 1 : 1;
              int gg = arr[i - 1] > arr[i] ? f + 1 : 1;
              f = ff;
              g = gg;
              ans = max({ans, f, g});
          }
          return ans;
      }
  };
  

• class Solution:
      def maxTurbulenceSize(self, arr: List[int]) -> int:
          ans = f = g = 1
          for a, b in pairwise(arr):
              ff = g + 1 if a < b else 1
              gg = f + 1 if a > b else 1
              f, g = ff, gg
              ans = max(ans, f, g)
          return ans
  
  

• func maxTurbulenceSize(arr []int) int {
  	ans, f, g := 1, 1, 1
  	for i, x := range arr[1:] {
  		ff, gg := 1, 1
  		if arr[i] < x {
  			ff = g + 1
  		}
  		if arr[i] > x {
  			gg = f + 1
  		}
  		f, g = ff, gg
  		ans = max(ans, max(f, g))
  	}
  	return ans
  }
  

• function maxTurbulenceSize(arr: number[]): number {
      let f = 1;
      let g = 1;
      let ans = 1;
      for (let i = 1; i < arr.length; ++i) {
          const ff = arr[i - 1] < arr[i] ? g + 1 : 1;
          const gg = arr[i - 1] > arr[i] ? f + 1 : 1;
          f = ff;
          g = gg;
          ans = Math.max(ans, f, g);
      }
      return ans;
  }
  
  

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