63. Unique Paths II

动态规划的问题，属于坐标型动态规划（二维）

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.

java

class Solution {    public int uniquePathsWithObstacles(int[][] obstacleGrid) {        int m = obstacleGrid.length;        int n = obstacleGrid[0].length;        int[][] f = new int[m][n];        for (int i = 0; i < m; i++) {            if (obstacleGrid[i][0] != 1) {                f[i][0] = 1;            } else {                break;            }        }        for (int j = 0; j < n; j++) {            if (obstacleGrid[0][j] != 1) {                f[0][j] = 1;            } else {                break;            }        }        for (int i = 1; i < m; i++) {            for (int j = 1; j < n; j++) {                if (obstacleGrid[i][j] == 0) {                    f[i][j] = f[i - 1][j] + f[i][j - 1];                } else {                    f[i][j] = 0;                }            }        }        return f[m - 1][n - 1];    }}