Given an m × n matrix of integers, find the length of the longest strictly increasing path.
From each cell, you can move in 4 directions to a cell with a strictly larger value.
With matrix:
9 9 4
6 6 8
2 1 1
Longest path: 1 → 2 → 6 → 9. Length = 4.
With [[3,4,5],[3,2,6],[2,2,1]]: longest is 1 → 2 → 3 → 4 → 5 → 6. Length = 6.
Constraints: .