Leetcode 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.

解题：

类似于Unique Paths，简单DP，状态转移方程：f[i][j] = f[i - 1][j] + f[i][j]

只是注意0，1问题，1的话f[i][j] = 0

代码：

class Solution {
public:
int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
int row = obstacleGrid.size();
if(!row) return 0;
int col = obstacleGrid[0].size();
vector<vector<int> > f(row, vector<int>(col, 0));
f[0][0] = !obstacleGrid[0][0];
for(int i = 0; i < row; i ++) {
for(int j = 0; j < col; j ++) {
if(obstacleGrid[i][j]) {
f[i][j] = 0;
continue;
}
if(i) f[i][j] += f[i - 1][j];
if(j) f[i][j] += f[i][j - 1];
}
}
return f[row - 1][col - 1];
}
};