Unique Paths II，uniquepathsii

Follow up for "Unique Paths":

Now consider if some obstacles are added to the grids. How many unique paths would there be?

An obstacle and empty space is marked as 1 and 0 respectively in the grid.

For example,

There is one obstacle in the middle of a 3x3 grid as illustrated below.

[
  [0,0,0],
  [0,1,0],
  [0,0,0]
]

The total number of unique paths is 2.

Note: m and n will be at most 100.

答案

public class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        if(obstacleGrid==null||obstacleGrid.length==0||obstacleGrid[0].length==0)
        {
            return 0;
        }
        int m=obstacleGrid.length;
        int n=obstacleGrid[0].length;
        int []number=new int[n];
        int row=m-1;
        int col=n-1;
        number[col]=obstacleGrid[row][col]==0?1:0;
        for(col=n-2;col>=0;col--)
        {
            number[col]=obstacleGrid[row][col]==0?number[col+1]:0;
        }
        for(row=m-2;row>=0;row--)
        {
            number[n-1]=obstacleGrid[row][n-1]==0?number[n-1]:0;
            for(col=n-2;col>=0;col--)
            {
                number[col]=obstacleGrid[row][col]==0?(number[col]+number[col+1]):0;
            }
        }
        return number[0];
    }
}