レビュー指摘を適用したコードを追加

Author: colorbox

21/4.cpp

@@ -0,0 +1,39 @@
+/**
+ * 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* mergeTwoLists(ListNode* list1, ListNode* list2) {
+        ListNode root = ListNode();
+        ListNode *current = &root;
+
+        ListNode *smaller = list1;
+        ListNode *bigger = list2;
+
+        while (smaller && bigger) {
+            if (smaller->val > bigger->val) {
+                swap(smaller, bigger);
+            }
+
+            current->next = smaller;
+            current = current->next;
+            smaller = smaller->next;
+        }
+
+        if (smaller) {
+            current->next = smaller;
+        }
+        if (bigger) {
+            current->next = bigger;
+        }
+
+        return root.next;
+    }
+};