Hard
Given an m x n integer matrix, return the length of the longest strictly increasing path. From a cell you may move up, down, left, or right (no diagonals or wrap-around).
Input: matrix = [[9,9,4],[6,6,8],[2,1,1]] Output: 4 Explanation: The path [1,2,6,9].
Input: matrix = [[3,4,5],[3,2,6],[2,2,1]] Output: 4