63. Unique Paths II

A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).

The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked 'Finish' in the diagram below).

Now consider if some obstacles are added to the grids. How many unique paths would there be?

An obstacle and space is marked as 1 and 0 respectively in the grid.

Example 1:

Input: obstacleGrid = [[0,0,0],[0,1,0],[0,0,0]]
Output: 2
Explanation: There is one obstacle in the middle of the 3x3 grid above.
There are two ways to reach the bottom-right corner:
1. Right -> Right -> Down -> Down
2. Down -> Down -> Right -> Right

Example 2:

Input: obstacleGrid = [[0,1],[0,0]]
Output: 1

Constraints:

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

# @lc code=start
using LeetCode

function unique_path_with_obstacles_63!(obstacleGrid::Vector{Vector{Int}})::Int
    m, n = length(obstacleGrid), length(obstacleGrid[1])
    obstacleGrid[1][1] = 1 - obstacleGrid[1][1]
    for i in 2:n
        obstacleGrid[1][i] = obstacleGrid[1][i] == 1 ? 0 : obstacleGrid[1][i - 1]
    end
    for i in 2:m
        obstacleGrid[i][1] = obstacleGrid[i][1] == 1 ? 0 : obstacleGrid[i - 1][1]
    end
    for i in 2:m
        for j in 2:n
            obstacleGrid[i][j] = if obstacleGrid[i][j] == 1
                0
            else
                obstacleGrid[i - 1][j] + obstacleGrid[i][j - 1]
            end
        end
    end
    return obstacleGrid[end][end]
end
function unique_path_with_obstacles_63(obstacleGrid::Vector{Vector{Int}})
    return unique_path_with_obstacles_63!(copy(obstacleGrid))
end
# @lc code=end

unique_path_with_obstacles_63 (generic function with 1 method)

This page was generated using DemoCards.jl and Literate.jl.