Unique Paths IIMar 29 '124573 / 11497
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) {
auto &a = obstacleGrid;
int n = a.size();
if (n == 0) return 0;
int m = a[0].size();
vector<int> res(m, 0);
if (a[0][0] == 0) res[0] = 1;
for (int i = 1; i < m; i++) {
if (res[i-1] > 0 && a[0][i] == 0) res[i] = res[i-1];
}
for (int i = 1; i < n; i++) {
if (res[0] == 0 || a[i][0] == 1) res[0] = 0;
for (int j = 1; j < m; j++) {
if (a[i][j] == 1) res[j] = 0;
else res[j] += res[j-1];
}
}
return res[m-1];
}
};