Leetcode•May 04, 2026
Unique Paths II
Hazrat Ali
Leetcode
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.
The testcases are generated so that the answer will be less than or equal to 2 * 109.
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
Solution
var uniquePathsWithObstacles = function(obstacleGrid) {
let m = obstacleGrid.length;
let n = obstacleGrid[0].length;
let dp = new Array(n).fill(0);
dp[0] = obstacleGrid[0][0] === 0 ? 1 : 0;
for (let i = 0; i < m; i++) {
for (let j = 0; j < n; j++) {
if (obstacleGrid[i][j] === 1) {
dp[j] = 0;
} else if (j > 0) {
dp[j] += dp[j - 1];
}
}
}
return dp[n - 1];
};