leetcode Unique Paths II

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.

I actually submitted the code with TLE using DFS. DP is the right solution:

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