LeetCode63 Unique Paths II

题目：

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. （Medium）

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.

分析：

上一题的follow-up，加上了障碍物，思路一样，只是障碍物处dp[i][j] = 0;

代码：

 1 class Solution {
 2 public:
 3     int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
 4         int m = obstacleGrid.size();
 5         int n = obstacleGrid[0].size();
 6         int dp[m][n];
 7         memset(dp,0,sizeof(dp));
 8         for (int i = 0; i < n; ++i) {
 9             if (obstacleGrid[0][i] == 1) {
10                 break;
11             }
12             dp[0][i] = 1;
13         }
14         for (int i = 0; i < m; ++i) {
15             if (obstacleGrid[i][0] == 1) {
16                 break;
17             }
18             dp[i][0] = 1;
19         }
20         for (int i = 1; i < m; ++i) {
21             for (int j = 1; j < n; ++j) {
22                 if (obstacleGrid[i][j] == 1) {
23                     dp[i][j] = 0;
24                 }
25                 else {
26                     dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
27                 }
28             }
29         }
30         return dp[m - 1][n - 1];
31     }
32 };

注：为什么这道题里dp[m][n] = {0}不能把二维数组初始化为0了......