1.最小基因变化

思路：bfs搜索回溯

python: 

class Solution:def minMutation(self, start: str, end: str, bank: List[str]) -> int:library = ['A','C', 'G','T']queue = [start]num = 0vis = set()while queue:size = len(queue)for i in range(size):cur = queue.pop(0)if cur == end:return num                for j in range(len(cur)):for letter in library:temp = cur[:j] + letter +cur[j+1:]if temp in bank and temp not in vis:queue.append(temp)vis.add(temp)num += 1return -1

c++:

class Solution {
public:int minMutation(string start, string end, vector<string>& bank) {string library = "ACGT";queue<string> queue_;queue_.push(start);int num = 0;unordered_set<string> vis;while(!queue_.empty()){int size = queue_.size();for(int i = 0; i < size; i++){string cur = queue_.front();queue_.pop();if(cur == end){return num;}for(int j = 0; j < cur.size(); j++){for(auto letter : library){string temp = cur.substr(0, j) + letter + cur.substr(j+1, cur.size() - j - 1);// cout<<temp<<endl;if(std::find(bank.begin(), bank.end(), temp) != bank.end() && vis.find(temp) == vis.end()){queue_.push(temp);vis.insert(temp);}}}}num ++ ;}return -1;}
};