Longest Increasing Path in a Matrix

Description

Given an m x n integers matrix, return the length of the longest increasing path in matrix.

From each cell, you can either move in four directions: left, right, up, or down. You may not move diagonally or move outside the boundary (i.e., wrap-around is not allowed).

For the matrix pictured above, the input matrix can be represented as a list of lists:

matrix = [[9,9,4],[6,6,8],[2,1,1]]
output = 4 # [1, 2, 6, 9]

def longestIncreasingPath(self, matrix)

    return 0