63.unique-paths-ii.java

/*
 * @lc app=leetcode id=63 lang=java
 *
 * [63] Unique Paths II
 */

// @lc code=start
class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int m = obstacleGrid.length;
        int n = obstacleGrid[0].length;
        int[][] dp = new int[m][n];

        //if there is a wall in first column
        for (int i = 0; i < m; i++) {
            if (obstacleGrid[i][0] == 1) {
                dp[i][0] = 0;
                break;
            } else {
                dp[i][0] = 1;
            }
        }
        //if there is a wall in the first row
        for (int i = 0; i < n; i++) {
            if (obstacleGrid[0][i] == 1) {
                dp[0][i] = 0;
                break;
            } else {
                dp[0][i] = 1;
            }
        }

        for (int i = 1; i < m; i++) {
            for (int j = 1; j < n; j++) {
                if (obstacleGrid[i][j] == 1) {
                    dp[i][j] = 0;
                } else {
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                }
            }
        }
        return dp[m - 1][n - 1];

    }
}
// @lc code=end