[Leetcode 63, Medium] Unique Paths II

Problem:

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

Analysis:

Solutions:

C++:

    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {        int m = obstacleGrid.size();        int n = obstacleGrid[0].size();        if(m == 0 && n == 0)            return 0;                    if(m == 0 || n == 0) {            return 1;        }                    vector<vector<int> > num_of_paths;        for(int row = 0; row < m; ++row) {            vector<int> new_row;            for(int col = 0; col < n; ++col)                new_row.push_back(1);                            num_of_paths.push_back(new_row);        }                for(int i = 0; i < n; ++i) {            if(obstacleGrid[0][i] == 1) {                for(int j = i; j < n; ++j)                    num_of_paths[0][j] = 0;                                    break;            }        }                for(int i = 0; i < m; ++i) {            if(obstacleGrid[i][0] == 1) {                for(int j = i; j < m; ++j)                    num_of_paths[j][0] = 0;                                    break;            }        }                for(int i = 1; i < m; ++i) {            for(int j = 1; j < n; ++j) {                if(obstacleGrid[i][j] == 1)                    num_of_paths[i][j] = 0;                else                    num_of_paths[i][j] = num_of_paths[i - 1][j] + num_of_paths[i][j - 1];            }        }                return num_of_paths[m - 1][n - 1];    }

Java:

Python: