rename folder to data_structures

data_structures/linkedlist_implentation_usingarray.cpp

@@ -0,0 +1,104 @@
+/* The difference between the pointer implementation of linked list and array
+ implementation of linked list:
+ 1. The NULL is represented by -1;
+ 2. Limited size. (in the following case it is 100 nodes at max). But we can
+ reuse the nodes that are to be deleted by again linking it bacj to the list.
+*/
+
+#include <iostream>
+using namespace std;
+struct Node {
+    int data;
+    int next;
+};
+Node AvailArray[100];  // array that will act as nodes of a linked list.
+int head = -1;
+int avail = 0;
+void initialise_list() {
+    for (int i = 0; i <= 98; i++) {
+        AvailArray[i].next = i + 1;
+    }
+    AvailArray[99].next = -1;  // indicating the end of the linked list.
+}
+
+int getnode()  // This will return the index of the first free node present in
+               // the avail list
+{
+    int NodeIndexToBeReturned = avail;
+    avail = AvailArray[avail].next;
+    return NodeIndexToBeReturned;
+}
+
+void freeNode(
+    int nodeToBeDeleted)  // This function when called will delete the node with
+                          // the index presented as an argument, and will put
+                          // back that node into the array.
+{
+    AvailArray[nodeToBeDeleted].next = avail;
+    avail = nodeToBeDeleted;
+}
+
+void insertAtTheBeginning(int data)  // The function will insert the given data
+                                     // into the front of the linked list.
+{
+    int newNode = getnode();
+    AvailArray[newNode].data = data;
+    AvailArray[newNode].next = head;
+    head = newNode;
+}
+
+void insertAtTheEnd(int data) {
+    int newNode = getnode();
+    int temp = head;
+    while (AvailArray[temp].next != -1) {
+        temp = AvailArray[temp].next;
+    }
+    // temp is now pointing to the end node.
+    AvailArray[newNode].data = data;
+    AvailArray[newNode].next = -1;
+    AvailArray[temp].next = newNode;
+}
+
+void display() {
+    int temp = head;
+    while (temp != -1) {
+        cout << AvailArray[temp].data << "->";
+        temp = AvailArray[temp].next;
+    }
+    cout << "-1" << endl;
+    ;
+}
+
+int main() {
+    initialise_list();
+    int x, y, z;
+    for (;;) {
+        cout << "1. Insert At The Beginning" << endl;
+        cout << "2. Insert At The End" << endl;
+        cout << "3. Display" << endl;
+        cout << "4.Exit" << endl;
+        cout << "Enter Your choice" << endl;
+        cin >> z;
+        switch (z) {
+        case 1:
+            cout << "Enter the number you want to enter" << endl;
+            cin >> x;
+            insertAtTheBeginning(x);
+            break;
+        case 2:
+            cout << "Enter the number you want to enter" << endl;
+            cin >> y;
+            insertAtTheEnd(y);
+            break;
+        case 3:
+            cout << "The linked list contains the following element in order"
+                 << endl;
+            display();
+            break;
+        case 4:
+            exit(0);
+        default:
+            cout << "The entered choice is not correct" << endl;
+        }
+    }
+}