{"id":823,"date":"2025-08-02T17:53:22","date_gmt":"2025-08-02T12:23:22","guid":{"rendered":"https:\/\/codeanddebug.in\/blog\/?p=823"},"modified":"2025-08-02T17:53:55","modified_gmt":"2025-08-02T12:23:55","slug":"unique-paths-ii","status":"publish","type":"post","link":"https:\/\/codeanddebug.in\/blog\/unique-paths-ii\/","title":{"rendered":"Unique Paths II | Leetcode 63 | All 4 DP Solutions"},"content":{"rendered":"\n

You are given an m x n<\/code> integer array grid<\/code>. There is a robot initially located at the top-left corner<\/strong> (i.e., grid[0][0]<\/code>). The robot tries to move to the bottom-right corner<\/strong> (i.e., grid[m - 1][n - 1]<\/code>). The robot can only move either down or right at any point in time.<\/p>\n\n\n\n

An obstacle and space are marked as 1<\/code> or 0<\/code> respectively in grid<\/code>. A path that the robot takes cannot include any<\/strong> square that is an obstacle.<\/p>\n\n\n\n

Return the number of possible unique paths that the robot can take to reach the bottom-right corner<\/em>.<\/p>\n\n\n\n

Here’s the [Problem Link<\/span><\/mark><\/a><\/strong>] to begin with.<\/p>\n\n\n\n

The testcases are generated so that the answer will be less than or equal to 2 * 109<\/sup><\/code>.<\/p>\n\n\n\n

Example 1:<\/strong><\/p>\n\n\n\n

\"\"\/<\/figure>\n\n\n\n
Input:<\/strong> obstacleGrid = [[0,0,0],[0,1,0],[0,0,0]]
Output:<\/strong> 2
Explanation:<\/strong> 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<\/pre>\n\n\n\n
Example 2:<\/strong><\/p>\n\n\n\n
\"\"\/<\/figure>\n\n\n\n
Input:<\/strong> obstacleGrid = [[0,1],[0,0]]
Output:<\/strong> 1<\/pre>\n\n\n\n
Constraints:<\/strong><\/p>\n\n\n\n