[leetcode]Unique Paths II

class Solution {
public:
int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
if(obstacleGrid.empty()) return 0;
int m = obstacleGrid.size();
int n = obstacleGrid[0].size();

vector<vector<int>> f(m, vector<int>(n, 0));

for(int j = 0; j < n; j++){
if(obstacleGrid[0][j] == 1){
break;
}else{
f[0][j] = 1;
}
}

for(int i = 0; i < m; i++){
if(obstacleGrid[i][0] == 1){
break;
}else{
f[i][0] = 1;
}
}

for(int i = 1; i < m; i++){
for(int j = 1; j < n; j++){
if(obstacleGrid[i][j] == 1){
f[i][j] = 0;
}else{
f[i][j] = f[i-1][j] + f[i][j-1];
}
}
}
return f[m-1][n-1];
}
};