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g1901_2000.s1901_find_a_peak_element_ii.readme.md Maven / Gradle / Ivy

1901\. Find a Peak Element II

Medium

A **peak** element in a 2D grid is an element that is **strictly greater** than all of its **adjacent** neighbors to the left, right, top, and bottom.

Given a **0-indexed** `m x n` matrix `mat` where **no two adjacent cells are equal**, find **any** peak element `mat[i][j]` and return _the length 2 array_ `[i,j]`.

You may assume that the entire matrix is surrounded by an **outer perimeter** with the value `-1` in each cell.

You must write an algorithm that runs in `O(m log(n))` or `O(n log(m))` time.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/06/08/1.png)

**Input:** mat = [[1,4],[3,2]]

**Output:** [0,1]

**Explanation:** Both 3 and 4 are peak elements so [1,0] and [0,1] are both acceptable answers.

**Example 2:**

**![](https://assets.leetcode.com/uploads/2021/06/07/3.png)**

**Input:** mat = [[10,20,15],[21,30,14],[7,16,32]]

**Output:** [1,1]

**Explanation:** Both 30 and 32 are peak elements so [1,1] and [2,2] are both acceptable answers.

**Constraints:**

*   `m == mat.length`
*   `n == mat[i].length`
*   `1 <= m, n <= 500`
*   1 <= mat[i][j] <= 105
*   No two adjacent cells are equal.