127. 单词接龙

https://leetcode.cn/problems/word-ladder/description/?envType=study-plan-v2&envId=top-interview-150

思路：这题好像和上一题 433. 最小基因变化 基本一样，都是通过bfs找最短路径。

class Solution {public int ladderLength(String beginWord, String endWord, List<String> wordList) {boolean exist = false;for(String s : wordList) {if(s.equals(endWord)) {exist = true;break;}}if(!exist) return 0;// 存储字符串s与endWord的最短路径HashMap<String, Integer> map = new HashMap<>();map.put(endWord, 0);map.put(beginWord, -1); // -1代表还没找到最短路径Queue<String> queue = new LinkedList<>();Queue<String> temp = new LinkedList<>();queue.add(endWord);int cnt = 1;while(!queue.isEmpty()) {cnt++;while(!queue.isEmpty()) {String s = queue.poll();// 初始状态能否走到s状态if(differ(beginWord, s) == 1) {return cnt;}for(String str : wordList) {if(!map.containsKey(str) && differ(str, s) == 1) {temp.add(str);map.put(str, cnt);}}}queue = temp;temp = new LinkedList<>();}return 0;}/*** 计算两个字符串之间的差异* @param s 被计算串* @param target 目标串* @return 差异的字符数*/public int differ(String s, String target) {int cnt = 0;for (int i = 0; i < s.length(); i++) {if (s.charAt(i) != target.charAt(i)) {cnt++;}}return cnt;}
}