Update 面试题02.07链表相交，添加C#版

problems/面试题02.07.链表相交.md

@@ -502,6 +502,20 @@ object Solution {
   }
 }
 ```
+### C#
+```C#
+public ListNode GetIntersectionNode(ListNode headA, ListNode headB)
+{
+    if (headA == null || headB == null) return null;
+    ListNode cur1 = headA, cur2 = headB;
+    while (cur1 != cur2)
+    {
+        cur1 = cur1 == null ? headB : cur1.next;
+        cur2 = cur2 == null ? headA : cur2.next;
+    }
+    return cur1;
+}
+```
 
 
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