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.
代码语言：javascript复制[
[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.
有障碍物的时候（obstacleGridi==1），将对应的dp置0（dpi=0）。
代码语言：javascript复制 public int uniquePathsWithObstacles(int[][] obstacleGrid) {
if (obstacleGrid == null || obstacleGrid[0] == null) {
return 0;
}
if (obstacleGrid[0][0] == 1) {
return 0;
}
int m = obstacleGrid.length;
int n = obstacleGrid[0].length;
int[][] dp = new int[m][n];
for (int y = 1; y < n; y ) {
if (obstacleGrid[0][y] == 0) {
dp[0][y] = 1;
} else {
break;
}
}
for (int x = 1; x < m; x ) {
if (obstacleGrid[x][0] == 0) {
dp[x][0] = 1;
} else {
break;
}
}
for (int y = 1; y < n; y ) {
for (int x = 1; x < m; x ) {
if (obstacleGrid[x][y] == 1) {
dp[x][y] = 0;
} else {
dp[x][y] = dp[x - 1][y] dp[x][y - 1];
}
}
}
return dp[m - 1][n - 1];
}
