[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

.

Note: m and n will be at most 100.

将obstacle标记为-1，其余基本跟上一题一样。

class Solution {
public:
int uniquePathsWithObstacles(vector<vector<int> > &obstacleGrid) {
int m = obstacleGrid.size();
int n = obstacleGrid[0].size();
int i, j;
for (i = 0; i < m; ++i) {
for (j = 0; j < n; ++j) {
obstacleGrid[i][j] = -obstacleGrid[i][j];
}
}
for (i = 0; i < m; ++i) {
if (obstacleGrid[i][0] == -1) break;
obstacleGrid[i][0] = 1;
}
for (j = 0; j < n; ++j) {
if (obstacleGrid[0][j] == -1) break;
obstacleGrid[0][j] = 1;
}
for (i = 1; i < m; ++i) {
for (j = 1; j < n; ++j) {
if (obstacleGrid[i][j] == -1) continue;
obstacleGrid[i][j] += (obstacleGrid[i-1][j] == -1) ? 0 : obstacleGrid[i-1][j];
obstacleGrid[i][j] += (obstacleGrid[i][j-1] == -1) ? 0 : obstacleGrid[i][j-1];
}
}
return (obstacleGrid[m-1][n-1] == -1) ? 0 : obstacleGrid[m-1][n-1];
}
};