Leetcode 62. Unique Paths

Count the number of distinct monotonic paths from the top-left to the bottom-right of an m×n grid when you may only move right or down. This is the classic lattice-path problem — the answer equals binomial coefficient C(m+n-2, m-1) (or can be computed with DP); m,n ≤ 100 and result ≤ 2·10^9.