Solution2.java

class Solution {
    public int uniquePathsWithObstacles(int[][] dp) {
        if (dp[0][0] == 1 || dp[dp.length - 1][dp[0].length - 1] == 1) return 0;
        for (int i = 1; i < dp.length; i ++) {
            if (dp[i][0] == 1) {
                dp[i][0] = -1;
                continue;
            }
            if (dp[i - 1][0] == -1) {
                dp[i][0] = -1;
            } else dp[i][0] = 1;
        }
        for (int i = 1; i < dp[0].length; i ++) {
            if (dp[0][i] == 1) {
                dp[0][i] = -1;
                continue;
            }
            if (dp[0][i - 1] == -1) {
                dp[0][i] = -1;
            } else dp[0][i] = 1;
        }
        for (int i = 1; i < dp.length; i ++) {
            for (int j = 1; j < dp[0].length; j ++) {
                if (dp[i][j] == 1) {
                    dp[i][j] = -1;
                } else if (dp[i][j - 1] == -1 && dp[i - 1][j] == -1) {
                    dp[i][j] = -1;
                } else if (dp[i][j - 1] == -1) {
                    dp[i][j] = dp[i - 1][j];
                } else if (dp[i - 1][j] == -1) {
                    dp[i][j] = dp[i][j - 1];
                } else {
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                }
            }
        }
        int res = dp[dp.length - 1][dp[0].length - 1];
        if (res == 0) return 1;
        if (res == -1) return 0;
        return res;
    }
}