题目：[752. 打开转盘锁](https://leetcode.cn/problems/open-the-lock/)
## 单向bfs
执行用时：204 ms, 在所有 C++ 提交中击败了40.14%的用户
内存消耗：40.3 MB, 在所有 C++ 提交中击败了25.63%的用户
```c++
class Solution {
public:
unordered_map> dights = {
{'0', {'9', '1'}},
{'1', {'0', '2'}},
{'2', {'1', '3'}},
{'3', {'2', '4'}},
{'4', {'3', '5'}},
{'5', {'4', '6'}},
{'6', {'5', '7'}},
{'7', {'6', '8'}},
{'8', {'7', '9'}},
{'9', {'8', '0'}}};
int openLock(vector& deadends, string target) {
unordered_set deads(deadends.begin(), deadends.end());
if (deads.count("0000")) return -1;
deque que = {"0000"};
unordered_map visited = {{"0000", 0}};
while (!que.empty()) {
string cur = que.front();
que.pop_front();
