63. Unique Paths II

class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        for(int i=0;i<obstacleGrid.length;i++)
            for(int j=0;j<obstacleGrid[0].length;j++)
                obstacleGrid[i][j]=-obstacleGrid[i][j];
        obstacleGrid[0][0]=obstacleGrid[0][0]>=0?1:0;
        for(int i=0;i<obstacleGrid.length;i++)
            for(int j=0;j<obstacleGrid[0].length;j++)
                if(obstacleGrid[i][j]>=0)
                    obstacleGrid[i][j]+=(i>0&&obstacleGrid[i-1][j]>=0?obstacleGrid[i-1][j]:0)+(j>0&&obstacleGrid[i][j-1]>=0?obstacleGrid[i][j-1]:0);
        return Math.max(obstacleGrid[obstacleGrid.length-1][obstacleGrid[0].length-1], 0);
    }
}