Update 面试题02.07.链表相交.md

problems/面试题02.07.链表相交.md

@@ -152,7 +152,7 @@ public class Solution {
 
 ### Python
 ```python
-
+（版本一）求长度，同时出发
 class Solution:
     def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> ListNode:
         lenA, lenB = 0, 0
@@ -178,7 +178,68 @@ class Solution:
                 curB = curB.next
         return None 
 ```
+```python
+（版本二）求长度，同时出发 （代码复用）
+class Solution:
+    def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> ListNode:
+        lenA = self.getLength(headA)
+        lenB = self.getLength(headB)
+        
+        # 通过移动较长的链表，使两链表长度相等
+        if lenA > lenB:
+            headA = self.moveForward(headA, lenA - lenB)
+        else:
+            headB = self.moveForward(headB, lenB - lenA)
+        
+        # 将两个头向前移动，直到它们相交
+        while headA and headB:
+            if headA == headB:
+                return headA
+            headA = headA.next
+            headB = headB.next
+        
+        return None
+    
+    def getLength(self, head: ListNode) -> int:
+        length = 0
+        while head:
+            length += 1
+            head = head.next
+        return length
+    
+    def moveForward(self, head: ListNode, steps: int) -> ListNode:
+        while steps > 0:
+            head = head.next
+            steps -= 1
+        return head
+```
+```python
+（版本三）等比例法
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
 
+class Solution:
+    def getIntersectionNode(self, headA: ListNode, headB: ListNode) -> ListNode:
+        # 处理边缘情况
+        if not headA or not headB:
+            return None
+        
+        # 在每个链表的头部初始化两个指针
+        pointerA = headA
+        pointerB = headB
+        
+        # 遍历两个链表直到指针相交
+        while pointerA != pointerB:
+            # 将指针向前移动一个节点
+            pointerA = pointerA.next if pointerA else headB
+            pointerB = pointerB.next if pointerB else headA
+        
+        # 如果相交，指针将位于交点节点，如果没有交点，值为None
+        return pointerA
+```
 ### Go
 
 ```go