Travel the Grid

What this grid-path-counting interview question tests

This is an easy combinatorial puzzle that appears in quant and trading interviews to assess how you handle constrained path-counting problems. It combines lattice-path enumeration with the practical constraint of an obstacle, requiring you to think clearly about inclusion–exclusion or conditional counting.

The core skill is recognizing that the shortest path from one corner to the opposite corner of a grid has a fixed length, and then accounting for the blocked crossroad. Candidates who solve this cleanly typically set up the problem by identifying all valid paths, then systematically subtract or condition on those that pass through the obstacle. The emphasis is on structured reasoning rather than brute-force enumeration.

• Lattice paths and Manhattan distance
• Combinatorial counting with restrictions
• Inclusion–exclusion principle
• Path decomposition techniques