Routes Across a Grid — Solution & Editorial
A route is a shuffle of H−1 downs and W−1 rights: C(H+W−2, H−1). Compute with factorials or an incremental product plus modular inverse.
Complexity: O(H + W)
A route is a shuffle of H−1 downs and W−1 rights: C(H+W−2, H−1). Compute with factorials or an incremental product plus modular inverse.
Complexity: O(H + W)