find-a-peak-element-ii

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Algorithms

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 <code>m x n</code> matrix <code>mat</code> where no two adjacent cells are equal, find any peak element <code>mat[i][j]</code> and return the length 2 array <code>[i,j]</code>.

You may assume that the entire matrix is surrounded by an outer perimeter with the value <code>-1</code> in each cell.

You must write an algorithm that runs in <code>O(m log(n))</code> or <code>O(n log(m))</code> time.

&nbsp;
Example 1:

<img alt="" src="https://assets.leetcode.com/uploads/2021/06/08/1.png" style="width: 206px; height: 209px;" />

<pre>
Input: mat = [[1,4],[3,2]]
Output: [0,1]
Explanation:&nbsp;Both 3 and 4 are peak elements so [1,0] and [0,1] are both acceptable answers.
</pre>

Example 2:

<img alt="" src="https://assets.leetcode.com/uploads/2021/06/07/3.png" style="width: 254px; height: 257px;" />

<pre>
Input: mat = [[10,20,15],[21,30,14],[7,16,32]]
Output: [1,1]
Explanation:&nbsp;Both 30 and 32 are peak elements so [1,1] and [2,2] are both acceptable answers.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>m == mat.length</code></li>
	<li><code>n == mat[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 500</code></li>
	<li><code>1 &lt;= mat[i][j] &lt;= 105</code></li>
	<li>No two adjacent cells are equal.</li>
</ul>

findPeakGrid

Find a Peak Element II

Find Peak Element

find-peak-element

寻找峰值

Find the Peaks

find-the-peaks

找出峰值

Array

Binary Search

Matrix

一个 2D 网格中的 峰值 是指那些 严格大于 其相邻格子(上、下、左、右)的元素。

给你一个 从 0 开始编号 的 <code>m x n</code> 矩阵 <code>mat</code> ，其中任意两个相邻格子的值都 不相同 。找出 任意一个 峰值 <code>mat[i][j]</code> 并 返回其位置 <code>[i,j]</code> 。

你可以假设整个矩阵周边环绕着一圈值为 <code>-1</code> 的格子。

要求必须写出时间复杂度为 <code>O(m log(n))</code> 或 <code>O(n log(m))</code> 的算法

&nbsp;

&nbsp;

示例 1:

<img alt="" src="https://assets.leetcode.com/uploads/2021/06/08/1.png" style="width: 206px; height: 209px;" />

<pre>
输入: mat = [[1,4],[3,2]]
输出: [0,1]
解释:&nbsp;3 和 4 都是峰值，所以[1,0]和[0,1]都是可接受的答案。
</pre>

示例 2:

<img alt="" src="https://assets.leetcode.com/uploads/2021/06/07/3.png" style="width: 254px; height: 257px;" />

<pre>
输入: mat = [[10,20,15],[21,30,14],[7,16,32]]
输出: [1,1]
解释:&nbsp;30 和 32 都是峰值，所以[1,1]和[2,2]都是可接受的答案。
</pre>

&nbsp;

提示：

<ul>
	<li><code>m == mat.length</code></li>
	<li><code>n == mat[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 500</code></li>
	<li><code>1 &lt;= mat[i][j] &lt;= 105</code></li>
	<li>任意两个相邻元素均不相等.</li>
</ul>