solve #224

Author: crumbs22

merge_two_sorted_lists.cpp

@@ -0,0 +1,44 @@
+#include <iostream>
+
+using namespace std;
+
+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) {
+            if (!list1)
+                return (list2);
+            if (!list2)
+                return (list1);
+    
+            ListNode ans_head = ListNode();
+            ListNode* tmp = &ans_head;
+    
+            while (list1 && list2) {
+                if (list1->val <= list2->val) {
+                    tmp->next = list1;
+                    list1 = list1->next;
+                    tmp = tmp->next;
+                }
+                else {
+                    tmp->next = list2;
+                    list2 = list2->next;
+                    tmp = tmp->next;
+                }
+            }
+            if (list1) {
+                tmp->next = list1;
+            }
+            else if (list2) {
+                tmp->next = list2;
+            }
+            return (ans_head.next);
+        }
+    };