From 8e7d9f579ca973454fdd11f6857f1bd29664db3a Mon Sep 17 00:00:00 2001
From: jianghongcheng <35664721+jianghongcheng@users.noreply.github.com>
Date: Thu, 1 Jun 2023 15:19:27 -0500
Subject: [PATCH] =?UTF-8?q?Update=200509.=E6=96=90=E6=B3=A2=E9=82=A3?=
 =?UTF-8?q?=E5=A5=91=E6=95=B0.md?=
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---
 problems/0509.斐波那契数.md | 38 ++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/problems/0509.斐波那契数.md b/problems/0509.斐波那契数.md
index 195b68ac..cdbf860c 100644
--- a/problems/0509.斐波那契数.md
+++ b/problems/0509.斐波那契数.md
@@ -230,17 +230,41 @@ class Solution:
         return dp[n]
 
 ```
-动态规划（版本二）
+态规划（版本二）
+```python 
+
+class Solution:
+    def fib(self, n: int) -> int:
+        if n <= 1:
+            return n
+        
+        dp = [0, 1]
+        
+        for i in range(2, n + 1):
+            total = dp[0] + dp[1]
+            dp[0] = dp[1]
+            dp[1] = total
+        
+        return dp[1]
+
+
+```
+动态规划（版本三）
 ```python 
 class Solution:
     def fib(self, n: int) -> int:
-        if n < 2:
+        if n <= 1:
             return n
-        a, b, c = 0, 1, 0
-        for i in range(1, n):
-            c = a + b
-            a, b = b, c
-        return c
+        
+        prev1, prev2 = 0, 1
+        
+        for _ in range(2, n + 1):
+            curr = prev1 + prev2
+            prev1, prev2 = prev2, curr
+        
+        return prev2
+
+
 
 
 ```