[Hash Map Program Addition ] --- Added the hashmap program.

Merge_Two_sorted_lists.cpp

@@ -0,0 +1,40 @@
+// 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) {
+        // Create a dummy node to serve as the start of the merged list
+        ListNode* dummy = new ListNode(-1);
+        ListNode* current = dummy;
+
+        // Traverse both lists
+        while (list1 != nullptr && list2 != nullptr) {
+            // Compare the values in both lists and append the smaller one
+            if (list1->val <= list2->val) {
+                current->next = list1;
+                list1 = list1->next;  // Move list1 pointer forward
+            } else {
+                current->next = list2;
+                list2 = list2->next;  // Move list2 pointer forward
+            }
+            current = current->next;  // Move the current pointer forward
+        }
+
+        // If one of the lists still has nodes left, append them
+        if (list1 != nullptr) {
+            current->next = list1;
+        } else {
+            current->next = list2;
+        }
+
+        // Return the next node after the dummy node, which is the head of the merged list
+        return dummy->next;
+    }
+};