题目：
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.
思路：
这道题跟Unique Paths的区别在于路线中有了障碍物，只需把障碍物处路线数变为0即可。
/**
* @param {number[][]} obstacleGrid
* @return {number}
*/
var uniquePathsWithObstacles = function(obstacleGrid) {
var f=[];
var m=obstacleGrid.length,n=obstacleGrid[0].length;
for(var i=0;i<m;i++){
f[i]=[];
} for(var i=0;i<m;i++){
if(obstacleGrid[i][0]==1){
f[i][0]=0;
for(var j=i+1;j<m;j++){
f[j][0]=0;
}
break
}else{
f[i][0]=1;
}
} for(var i=0;i<n;i++){
if(obstacleGrid[0][i]==1){
f[0][i]=0;
for(var j=i+1;j<n;j++){
f[0][j]=0;
}
break;
}else{
f[0][i]=1
}
} for(var i=1;i<m;i++){
for(var j=1;j<n;j++){
if(obstacleGrid[i][j]==1){
f[i][j]=0;
}else{
f[i][j]=f[i-1][j]+f[i][j-1];
}
}
} return f[m-1][n-1]; };