leetcode@ [62/63] Unique Paths II

 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 };