Merge pull request #33 from Frisk0316/Frisk0316-patch-33

Create 1721. Swapping Nodes in a Linked List

Author: Frisk0316

1721. Swapping Nodes in a Linked List

@@ -0,0 +1,36 @@
+// 2023.05.15 Leetcode Daily Challenge
+// wrote by C++
+// Runtime beats 90.85%
+// Memory beats 70.53%
+
+
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+ 
+class Solution {
+public:
+    ListNode* swapNodes(ListNode* head, int k) {
+    ListNode *n1 = nullptr;
+    ListNode *n2 = nullptr;
+    
+    for (auto p = head; p != nullptr; p = p->next) {
+        n2 = n2 == nullptr ? nullptr : n2->next;
+        if (--k == 0) {
+            n1 = p;
+            n2 = head;
+        }
+    }
+    
+	 // The problem description specifically asks to swap values, not nodes themselves. 
+    swap(n1->val, n2->val);
+    return head;        
+    }
+};