// Unique Paths
//Runtime: 0 ms, faster than 100.00% of Java online submissions for Unique Paths.
//Memory Usage: 32.8 MB, less than 5.10% of Java online submissions for Unique Paths.

class Solution {
    public int uniquePaths(int m, int n) {

        int[][] matrix = new int[n][m];

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

        return matrix[n - 1][m - 1];
    }
}

// Unique Paths II
//Runtime: 0 ms, faster than 100.00% of Java online submissions for Unique Paths II.
//Memory Usage: 38 MB, less than 100.00% of Java online submissions for Unique Paths II.

class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int n = obstacleGrid.length;
        int m = obstacleGrid[0].length;

        int[][] matrix = new int[n][m];

        for (int i = 0; i < n; i++) {
            if (obstacleGrid[i][0] == 1) {
                matrix[i][0] = 0;
                break;
            }
            matrix[i][0] = 1;
        }

        for (int j = 0; j < m; j++) {
            if (obstacleGrid[0][j] == 1) {
                matrix[0][j] = 0;
                break;
            }
            matrix[0][j] = 1;
        }

        for (int i = 1; i < n; i++) {
            for (int j = 1; j < m; j++) {
                matrix[i][j] = obstacleGrid[i][j] == 1 ? 0 : matrix[i - 1][j] + matrix[i][j - 1];
            }
        }

        return matrix[n - 1][m - 1];
    }
}