Create swapping-nodes-in-a-linked-list.cpp

Author: kamyu104

C++/swapping-nodes-in-a-linked-list.cpp

@@ -0,0 +1,30 @@
+// Time:  O(n)
+// Space: O(1)
+
+/**
+ * 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 *left = nullptr, *right = nullptr;
+        for (auto curr = head; curr; curr = curr->next) {
+            if (right) {
+                right = right->next;
+            }
+            if (--k == 0) {
+                left = curr;
+                right = head;
+            }
+        }
+        swap(left->val, right->val);
+        return head;
+    }
+};