59. Unique Paths II

MediumDynamic Programming

You are given an m x n integer array grid. There is a robot 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. An obstacle and space are marked as 1 or 0 respectively in grid. A path that the robot takes cannot include any square that is an obstacle. Return the number of possible unique paths that the robot can take to reach the bottom-right corner.

Examples

Input: [[0,0,0],[0,1,0],[0,0,0]]

Output: 2

Explanation: The central obstacle leaves 2 unique paths.

Constraints

m == obstacleGrid.length
n == obstacleGrid[i].length
1 <= m, n <= 100
obstacleGrid[i][j] is 0 or 1.

Run checks all cases above. Submit evaluates all test cases.