Added the insert element in LL code in c++.

Linked List/Linked List.md

@@ -0,0 +1,64 @@
+# Description: For a given Singly LinkedList, insert a node at the beginning of the linked list.
+
+//Input: List = 10->20->30->40->null, Node = 0
+//Output: 0->10->20->30->40->null
+//Explanation: Inserted the given node at the beginning of the linked list.
+
+//Example 2:
+//Input: List = 100->200->300->null, Node =700
+//Output: 700->100->200->300->null
+//Explanation: Inserted the given node at the beginning of the linked list.
+
+```cpp
+#include <bits/stdc++.h>
+
+using namespace std;
+
+class ListNode {
+  public:
+    int val;
+  ListNode * next;
+  ListNode(int x) {
+    val = x;
+    next = NULL;
+  }
+};
+
+void PrintList(ListNode * head) // Function to print the LinkedList
+{
+  ListNode * curr = head;
+  for (; curr != NULL; curr = curr -> next)
+    cout << curr -> val << "-->";
+  cout << "null" << endl;
+}
+
+ListNode * InsertatFirst(int value, ListNode * head) {
+
+  // Step1 : creating a new Node with the given val
+  ListNode * newnode = new ListNode(value);
+
+  // Step2 : Making next of newly created Node to point the head of LinkedList
+  newnode -> next = head;
+
+  // Making the newly created Node as head
+  head = newnode;
+  return head;
+}
+
+int main() {
+  ListNode * head = NULL; // head of the LinkedList
+  head = InsertatFirst(40, head);
+  head = InsertatFirst(30, head);
+  head = InsertatFirst(20, head);
+  head = InsertatFirst(10, head);
+  cout << "LinkedList before inserting 0 at beginning : " << endl;
+  PrintList(head);
+  head = InsertatFirst(0, head);
+  cout << "LinkedList after inserting 0 at beginning : " << endl;
+  PrintList(head);
+  return 0;
+}
+
+#Time Complexity:  O(1) Because we are just Manipulating the links, which is a constant operation.
+
+#Space Complexity: O(1) We are not using any extra space.