From 18cf68855f0008c9388e1ffc87a7699ce28f37e5 Mon Sep 17 00:00:00 2001
From: SquidSpirit <squid@squidspirit.com>
Date: Thu, 13 Feb 2025 23:45:54 +0800
Subject: [PATCH] feat: 21_merge_two_sorted_lists

---
 21_merge_two_sorted_lists/main.cpp | 48 ++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)
 create mode 100644 21_merge_two_sorted_lists/main.cpp

diff --git a/21_merge_two_sorted_lists/main.cpp b/21_merge_two_sorted_lists/main.cpp
new file mode 100644
index 0000000..5421846
--- /dev/null
+++ b/21_merge_two_sorted_lists/main.cpp
@@ -0,0 +1,48 @@
+#include <bits/stdc++.h>
+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 && !list2) {
+            return nullptr;
+        }
+
+        ListNode *result = new ListNode{0, nullptr};
+        ListNode *currentNode = result;
+        ListNode *lastNode = nullptr;
+
+        ListNode *current1 = list1;
+        ListNode *current2 = list2;
+
+        while (current1 != nullptr || current2 != nullptr) {
+            int val1 = current1 != nullptr ? current1->val : INT32_MAX;
+            int val2 = current2 != nullptr ? current2->val : INT32_MAX;
+
+            if (val1 <= val2) {
+                currentNode->val = val1;
+                current1 = current1->next;
+            } else {
+                currentNode->val = val2;
+                current2 = current2->next;
+            }
+
+            currentNode->next = new ListNode{0, nullptr};
+            lastNode = currentNode;
+            currentNode = currentNode->next;
+        }
+
+        lastNode->next = nullptr;
+        delete currentNode;
+
+        return result;
+    }
+};