Unique Paths II

    public int uniquePathsWithObstacles(int[][] obstacleGrid) {        // Start typing your Java solution below        // DO NOT write main() function        int m = obstacleGrid.length;        if(m == 0) return 0;        int n = obstacleGrid[0].length;        int[][] dp = new int[m][n];        if(obstacleGrid[0][0] == 1) {            return 0;        }else{            dp[0][0] = 1;        }        for(int i = 1; i < m; i++) {            if(obstacleGrid[i][0] != 1 && dp[i - 1][0] != 0) {                dp[i][0] = 1;            }else {                dp[i][0] = 0;            }        }        for(int j = 1; j < n; j++) {            if(obstacleGrid[0][j] != 1 && dp[0][j - 1] != 0) {                dp[0][j] = 1;            }else {                dp[0][j] = 0;            }        }        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];    }    public int uniquePathsWithObstacles(int[][] obstacleGrid) {        // Start typing your Java solution below        // DO NOT write main() function        int m = obstacleGrid.length;        if(m == 0) return 0;        int n = obstacleGrid[0].length;        int[][] dp = new int[2][n];        if(obstacleGrid[0][0] == 1) {            return 0;        }else{            dp[0][0] = 1;        }        for(int i = 1; i < n; i++) {            if(obstacleGrid[0][i] != 1 && dp[0][i - 1] != 0) {                dp[0][i] = 1;            }else {                dp[0][i] = 0;            }        }        int flag = 0;        for(int i = 1; i < m; i++) {            flag = i & 1;            if(obstacleGrid[i][0] == 1 || dp[flag ^ 1][0] == 0) {                dp[flag][0] = 0;            }else {                dp[flag][0] = 1;            }            for(int j = 1; j < n; j++) {                if(obstacleGrid[i][j] == 1) {                    dp[flag][j] = 0;                }else {                    dp[flag][j] = dp[flag ^ 1][j] + dp[flag][j - 1];                }            }        }        return dp[flag][n - 1];    }