Update 0509.斐波那契数.md

problems/0509.斐波那契数.md

@@ -203,18 +203,9 @@ class Solution {
 ```
 
 ### Python 
+动态规划（版本一）
 ```python 
-class Solution:
-    def fib(self, n: int) -> int:
-        if n < 2:
-            return n
-        a, b, c = 0, 1, 0
-        for i in range(1, n):
-            c = a + b
-            a, b = b, c
-        return c
 
-# 动态规划 (注释版。无修饰)
 class Solution:
     def fib(self, n: int) -> int:
 
@@ -238,7 +229,24 @@ class Solution:
         # 返回答案
         return dp[n]
 
-# 递归实现
+```
+动态规划（版本二）
+```python 
+class Solution:
+    def fib(self, n: int) -> int:
+        if n < 2:
+            return n
+        a, b, c = 0, 1, 0
+        for i in range(1, n):
+            c = a + b
+            a, b = b, c
+        return c
+
+
+```
+递归（版本一）
+```python 
+
 class Solution:
     def fib(self, n: int) -> int:
         if n < 2: