63. 不同路径 II

 1 class Solution 
 2 {
 3 public:
 4     int uniquePathsWithObstacles(vector<vector<int>>& nums) 
 5     {
 6         int m = nums.size();
 7         int n = nums[0].size();
 8 
 9         //起点或终点被堵死，直接返回0；
10         if(nums[0][0] == 1 || nums[m - 1][n - 1] == 1) return 0;
11 
12         vector<vector<long long>> dp(m,vector<long long>(n,0));
13         for(int i = 0;i < m;i ++) //初始化第一列
14         {
15             if(nums[i][0] == 0) dp[i][0] = 1;
16             else break;
17         }
18 
19         for(int j = 1;j < n;j ++) //初始化第一行
20         {
21             if(nums[0][j] == 0) dp[0][j] = 1;
22             else break;
23         }
24 
25         for(int i = 1;i < m;i ++)
26         {
27             for(int j = 1;j < n;j ++)
28             {
29                 if(nums[i][j] == 0) dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
30             }
31         }
32         return dp[m - 1][n - 1];
33     }
34 };