README.md

Unique Paths II

Solution 1

Two Dimensional Array

/**
 * Question   : 63. Unique Paths II
 * Complexity : Time: O(m*n) ; Space: O(m*n)
 * Topics     : DP
 */
class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int m = obstacleGrid.length;
        int n = obstacleGrid[0].length;

        int[][] dp = new int[m][n];
        if (obstacleGrid[0][0] == 0) {
            dp[0][0] = 1;
        }

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