update exercises

data/3.算法高阶/2.leetcode-哈希表/7.126-单词接龙 II/solution.md

@@ -22,13 +22,11 @@
 <strong>输出：</strong>[["hit","hot","dot","dog","cog"],["hit","hot","lot","log","cog"]]
 
 <strong>解释：</strong>存在 2 种最短的转换序列：
-
+</pre>
+```
 "hit" -> "hot" -> "dot" -> "dog" -> "cog"
-
 "hit" -> "hot" -> "lot" -> "log" -> "cog"
-
-</pre>
-
+```
 <p><strong>示例 2：</strong></p>
 
 <pre>