Update 0042.接雨水.md

修改代码格式

Author: hailincai

problems/0042.接雨水.md

@@ -422,7 +422,8 @@ class Solution {
 
 单调栈法
 ```java
-    public int trapMonoStack(int[] height){
+class Solution {
+    public int trap(int[] height){
         int size = height.length;
 
         if (size <= 2) return 0;
@@ -463,6 +464,7 @@ class Solution {
 
         return sum;
     }
+}
 ```
 
 Python: