Unique Paths II

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.

class Solution {public:    int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        int size = obstacleGrid.size();        if (size < 1) {            return 0;        }        if(obstacleGrid[0][0] == 0) {           obstacleGrid[0][0] = 1;        } else {            obstacleGrid[0][0] = 0;        }                for (int i = 0; i < size; ++i) {            for (int j = 0; j < obstacleGrid[0].size(); ++j) {                if (i == 0 && j > 0) {                    if (obstacleGrid[i][j] == 0) {                       obstacleGrid[i][j] = obstacleGrid[i][j-1];                    } else {                        obstacleGrid[i][j] = 0;                    }                 }                                  if (j == 0 && i > 0) {                     if (obstacleGrid[i][j] == 0) {                         obstacleGrid[i][j] = obstacleGrid[i-1][j];                     } else {                         obstacleGrid[i][j] = 0;                     }                 }                                  if (j > 0 && i > 0) {                     if (obstacleGrid[i][j] == 0) {                         obstacleGrid[i][j] = obstacleGrid[i][j-1] + obstacleGrid[i-1][j];                     } else {                         obstacleGrid[i][j] = 0;                     }                 }            }        }        return obstacleGrid[size - 1][obstacleGrid[0].size() - 1];            }};