1 class Solution {
2 public:
3 int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
4 if(obstacleGrid.size()==0 || obstacleGrid[0].size()==0) return 0;
5 int m = obstacleGrid.size(), n = obstacleGrid[0].size();
6 if(obstacleGrid[m-1][n-1]==1) return 0;
7
8 vector<vector<int> > dp(m);
9 for(int i=0;i<dp.size();++i) dp[i].resize(n);
10 for(int i=0;i<dp.size();++i){
11 for(int j=0;j<dp[i].size();++j) dp[i][j]=0;
12 }
13
14 dp[0][0] = (obstacleGrid[0][0]==1) ? 0 : 1;
15 for(int i=1;i<dp.size();++i){
16 if(dp[i-1][0] && !obstacleGrid[i][0]) dp[i][0] = 1;
17 }
18 for(int j=1;j<dp[0].size();++j){
19 if(dp[0][j-1] && !obstacleGrid[0][j]) dp[0][j] = 1;
20 }
21 for(int i=1;i<dp.size();++i){
22 for(int j=1;j<dp[i].size();++j){
23 if(i>=1 && !obstacleGrid[i-1][j]) dp[i][j] += dp[i-1][j];
24 if(j>=1 && !obstacleGrid[i][j-1]) dp[i][j] += dp[i][j-1];
25 }
26 }
27
28 return dp[m-1][n-1];
29 }
30 };
