description:
https://leetcode.com/problems/unique-paths/
机器人从一堆方格的左上角走到右下角，只能往右或者往下走 ，问有几种走法，这个加了难度，在矩阵中加了障碍物
Note:
Example:
Example 1:
Input:
[
[0,0,0],
[0,1,0],
[0,0,0]
]
Output: 2
Explanation:
There is one obstacle in the middle of the 3x3 grid above.
There are two ways to reach the bottom-right corner:
1. Right -> Right -> Down -> Down
2. Down -> Down -> Right -> Right
answer:
class Solution {
public:
int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
if (obstacleGrid.empty() || obstacleGrid[0].empty() || obstacleGrid[0][0] == 1) return 0;
int m = obstacleGrid.size(), n = obstacleGrid[0].size();
vector<vector<long>> dp(m + 1, vector<long>(n + 1, 0)); //比实际大一圈是为了处理左边和上边两个边的边缘问题
dp[0][1] = 1; // 初始化
for (int i = 1; i <= m; ++i) {
for (int j = 1; j <= n; ++j) {
if (obstacleGrid[i - 1][j - 1] != 0) continue; //如果是障碍则略过
dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
}
}
return dp[m][n];
}
};
relative point get√：
hint :
动态规划