Description
There is a robot on an m x n grid. The robot is initially located at the top-left corner (i.e., grid[0][0]). The robot tries to move to the bottom-right corner (i.e., grid[m - 1][n - 1]). The robot can only move either down or right at any point in time.
Given the two integers m and n, return the number of possible unique paths that the robot can take to reach the bottom-right corner.
The test cases are generated so that the answer will be less than or equal to 2 * 109.
Example 1:
Input: m = 3, n = 7 Output: 28
Example 2:
Input: m = 3, n = 2 Output: 3 Explanation: From the top-left corner, there are a total of 3 ways to reach the bottom-right corner: 1. Right -> Down -> Down 2. Down -> Down -> Right 3. Down -> Right -> Down
Constraints:
1 <= m, n <= 100
Solution
Python3
class Solution:
def uniquePaths(self, m: int, n: int) -> int:
grid = [[0] * n for _ in range(m)]
for i in range(m):
grid[i][0] = 1
for j in range(n):
grid[0][j] = 1
for i in range(1, m):
for j in range(1, n):
grid[i][j] += grid[i - 1][j] + grid[i][j - 1]
return grid[m - 1][n - 1]