Find a Peak Element II
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
1 4 3 2
Input
mat = [[1,4],[3,2]]Output
[0,1]Both 3 and 4 are peak elements, so [1,0] and [0,1] are both acceptable answers.
Example 2
10 20 15 21 30 14 7 16 32
Input
mat = [[10,20,15],[21,30,14],[7,16,32]]Output
[1,1]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] <= 10^5
- No two adjacent cells are equal.