LeetCode 62 Unique Paths - Implementation

Fill DP table row by row. Only need previous row.

def uniquePaths(m, n): dp = [1] * n

for i in range(1, m):
    for j in range(1, n):
        dp[j] = dp[j] + dp[j - 1]

return dp[n - 1]

$O(m \times n)$ time, $O(n)$ space.