【LeetCode】063. Unique Paths II

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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-];
}
};