Solution

CMakeLists.txt

@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.21)
+project(merge_two_sorted_linked_lists)
+
+set(CMAKE_CXX_STANDARD 14)
+
+add_executable(merge_two_sorted_linked_lists main.cpp)

main.cpp

@@ -0,0 +1,164 @@
+#include <iostream>
+#include <fstream>
+#include <string>
+
+using namespace std;
+
+class SinglyLinkedListNode {
+    public:
+        int data;
+        SinglyLinkedListNode *next;
+
+        SinglyLinkedListNode(int node_data) {
+            this->data = node_data;
+            this->next = nullptr;
+        }
+};
+
+class SinglyLinkedList {
+    public:
+        SinglyLinkedListNode *head;
+        SinglyLinkedListNode *tail;
+
+        SinglyLinkedList() {
+            this->head = nullptr;
+            this->tail = nullptr;
+        }
+
+        void insert_node(int node_data) {
+            SinglyLinkedListNode* node = new SinglyLinkedListNode(node_data);
+
+            if (!this->head) {
+                this->head = node;
+            } else {
+                this->tail->next = node;
+            }
+
+            this->tail = node;
+        }
+};
+
+void print_singly_linked_list(SinglyLinkedListNode* node, string sep, ofstream& fout) {
+    while (node) {
+        fout << node->data;
+
+        node = node->next;
+
+        if (node) {
+            fout << sep;
+        }
+    }
+}
+
+void free_singly_linked_list(SinglyLinkedListNode* node) {
+    while (node) {
+        SinglyLinkedListNode* temp = node;
+        node = node->next;
+
+        free(temp);
+    }
+}
+
+// Complete the mergeLists function below.
+
+/*
+ * For your reference:
+ *
+ * SinglyLinkedListNode {
+ *     int data;
+ *     SinglyLinkedListNode* next;
+ * };
+ *
+ */
+SinglyLinkedListNode* mergeLists(SinglyLinkedListNode* head1, SinglyLinkedListNode* head2) {
+
+    if (head1 == nullptr) {
+        return head2;
+    }
+    if (head2 == nullptr) {
+        return head1;
+    }
+
+    auto head_new = head1;
+    if (head_new->data > head2->data) {
+        head_new = head2;
+        head2 = head2->next;
+    } else {
+        head1 = head1->next;
+    }
+
+    auto iter = head_new;
+
+    while (1) {
+        if (head1 == nullptr) {
+            iter->next = head2;
+            break;
+        }
+        if (head2 == nullptr) {
+            iter->next = head1;
+            break;
+        }
+
+        if (head1->data <= head2->data) {
+            iter->next = head1;
+            head1 = head1->next;
+        } else {
+            iter->next = head2;
+            head2 = head2->next;
+        }
+
+        iter = iter->next;
+    }
+
+    return head_new;
+}
+
+int main()
+{
+    ofstream fout(getenv("OUTPUT_PATH"));
+
+    int tests;
+    cin >> tests;
+    cin.ignore(numeric_limits<streamsize>::max(), '\n');
+
+    for (int tests_itr = 0; tests_itr < tests; tests_itr++) {
+        SinglyLinkedList* llist1 = new SinglyLinkedList();
+
+        int llist1_count;
+        cin >> llist1_count;
+        cin.ignore(numeric_limits<streamsize>::max(), '\n');
+
+        for (int i = 0; i < llist1_count; i++) {
+            int llist1_item;
+            cin >> llist1_item;
+            cin.ignore(numeric_limits<streamsize>::max(), '\n');
+
+            llist1->insert_node(llist1_item);
+        }
+
+      	SinglyLinkedList* llist2 = new SinglyLinkedList();
+
+        int llist2_count;
+        cin >> llist2_count;
+        cin.ignore(numeric_limits<streamsize>::max(), '\n');
+
+        for (int i = 0; i < llist2_count; i++) {
+            int llist2_item;
+            cin >> llist2_item;
+            cin.ignore(numeric_limits<streamsize>::max(), '\n');
+
+            llist2->insert_node(llist2_item);
+        }
+
+        SinglyLinkedListNode* llist3 = mergeLists(llist1->head, llist2->head);
+
+        print_singly_linked_list(llist3, " ", fout);
+        fout << "\n";
+
+        free_singly_linked_list(llist3);
+    }
+
+    fout.close();
+
+    return 0;
+}