063 - 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.

int uniquePathsWithObstacles(int** grid, int row, int col)
{
int i, j;

if (!row || !col) return 0;
for (i = 0; i < col; i++) {
grid[0][i] = grid[0][i] ? -1 : 1;
if (i && grid[0][i - 1] == -1) grid[0][i] = -1;
}
for (i = 1; i < row; i++) {
grid[i][0] = grid[i][0] ? -1 : 1;
if (grid[i - 1][0] == -1) grid[i][0] = -1;
}
for (i = 1; i < row; i++)
for (j = 1; j < col; j++) {
if (grid[i][j] == 1) {
grid[i][j] = -1;
continue;
}
if (grid[i][j - 1] > 0) grid[i][j] += grid[i][j - 1];
if (grid[i - 1][j] > 0) grid[i][j] += grid[i - 1][j];
//if (!grid[i][j]) grid[i][j] = -1;
}

return grid[row - 1][col - 1] > 0 ? grid[row - 1][col - 1] : 0;
}