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：

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

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......