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.
代码：
1 vector<vector<int> >result; 2 int search(int sx, int sy, int ex, int ey, vector<vector<int> > &obstacleGrid){ 3 if(sx > ex || sy > ey || obstacleGrid[sx][sy] == 1) 4 return 0; 5 if(result[sx][sy] != -1) 6 return result[sx][sy]; 7 if(sx == ex && sy == ey) 8 return 1; 9 result[sx][sy] = search(sx+1, sy, ex, ey, obstacleGrid) + search(sx, sy+1, ex, ey, obstacleGrid); 10 return result[sx][sy]; 11 } 12 int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) { 13 // IMPORTANT: Please reset any member data you declared, as 14 // the same Solution instance will be reused for each test case. 15 result.clear(); 16 int m = obstacleGrid.size(); 17 if(m == 0) 18 return 0; 19 int n = obstacleGrid[0].size(); 20 if(n == 0) 21 return 0; 22 int i,j; 23 for(i = 0; i < m; i++){ 24 vector<int> tmp(n, -1); 25 result.push_back(tmp); 26 } 27 return search(0, 0, m-1, n-1, obstacleGrid); 28 }