leetcode Unique Paths II-白红宇

leetcode Unique Paths II

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发布时间：2019-05-26

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Unique Paths II

Total Accepted: 2092

Total Submissions: 8049

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];  }};