28_leetcode_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.

int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {

if(obstacleGrid.size() == 0 || obstacleGrid[0].size() == 0)
return 0;

int rows = (int)obstacleGrid.size();
int columns = (int)obstacleGrid[0].size();

vector<int> path(columns, 0);

for(int i = 0; i < rows; i++)
{
for(int j = 0; j < columns; j++)
{
if(i == 0 && j == 0)
{
if(obstacleGrid[i][j] == 1)
{
path[0] = 0;
}
else
{
path[0] = 1;
}
}
else if(i == 0)
{
if(obstacleGrid[i][j] == 1)
{
path[j] = 0;
}
else
{
path[j] = path[j-1];
}
}
else if(j == 0)
{
if(obstacleGrid[i][j] == 1)
{
path[0] = 0;
}
else
{
path[0] = path[0];
}
}
else
{
if(obstacleGrid[i][j] == 1)
{
path[j] = 0;
}
else
{
path[j] = path[j-1] + path[j];
}
}
}
}

return path[columns-1];
}