Unique Paths II

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.

题目大意：给定一个矩阵，0代表可以走，1代表障碍物不可走，求出从左上角到右下角的所有可能路径数量

题目难度：Medium

/**

• Created by gzdaijie on 16/5/27
• 到达阻碍物的路径为0

• 在第0行,和第0列,到达障碍物及障碍物之后的节点路径也为0 */ public class Solution { public int uniquePathsWithObstacles(int[][] obstacleGrid) {

   int m = obstacleGrid.length;
   if (m < 1) return 0;
   int n = obstacleGrid[0].length;
   if (n < 1) return 0;
  
   int[][] result = new int[m][n];
  
   for (int i = 0; i < m && obstacleGrid[i][0] == 0; i++) result[i][0] = 1;
  
   for (int i = 0; i < n && obstacleGrid[0][i] == 0; i++) result[0][i] = 1;
  
   for (int i = 1; i < m; i++) {
       for (int j = 1; j < n; j++) {
           result[i][j] = obstacleGrid[i][j] == 0 ? result[i - 1][j] + result[i][j - 1] : 0;
       }
   }
  
   return result[m - 1][n - 1];
  

  } }