【LeetCode】063. Unique Paths II

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.

题解：

Solution 1 ()(未优化）

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        if(obstacleGrid.empty() || obstacleGrid[].empty()) return ;
        int m = obstacleGrid.size(), n = obstacleGrid[].size();
        vector<int> dp(n,);
        dp[] = ;
        for(int i=; i<m; ++i) {
            for(int j=; j<n; ++j) {
                if(obstacleGrid[i][j] == )
                    dp[j] = dp[j-];
                else dp[j] += dp[j-];
            }
        }
        return dp[n-];
    }
};

Solution 2 ()

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        if(obstacleGrid.empty() || obstacleGrid[].empty()) return ;
        int m = obstacleGrid.size(), n = obstacleGrid[].size();
        vector<int> dp(n,);
        dp[] = ;
        for(int i=; i<m; ++i) {
            for(int j=; j<n; ++j) {
                if(obstacleGrid[i][j] == )
                    dp[j] = ;
                else {
                    if(j > )
                        dp[j] += dp[j-];
                }
            }
        }
        return dp[n-];
    }
};