Search⌘ K
AI Features
Home
Courses
Grokking the Coding Interview Patterns

Solution: Unique Paths III

Explore how backtracking solves Unique Paths III by recursively exploring valid four-directional paths in a grid. Understand marking visited squares and backtracking to ensure all empty squares are visited exactly once before reaching the end square.

We'll cover the following...

Statement

You are given a  m×nm \times n  integer array, grid, where each cell, grid[i][j], can have one of the following values:

  • 1 indicates the starting point. There is exactly one such square.

  • 2 marks the ending point. There is exactly one such square.

  • 0 represents empty squares that can be walked over.

  • -1 represents obstacles that cannot be crossed.

Your task is to return the total number of unique four-directional paths from the starting square (1) to the ending square (2), such that every empty square is visited ...