rename folder to data_structures

data_structures/queue_using_linkedlist.cpp

@@ -0,0 +1,86 @@
+/*
+    Write a program to implement Queue using linkedlist.
+*/
+#include <iostream>
+
+struct linkedlist {
+    int data;
+    linkedlist *next;
+};
+class stack_linkedList {
+ public:
+    linkedlist *front;
+    linkedlist *rear;
+
+    stack_linkedList() { front = rear = NULL; }
+    void enqueue(int);
+    int dequeue();
+    void display();
+};
+void stack_linkedList::enqueue(int ele) {
+    linkedlist *temp = new linkedlist();
+    temp->data = ele;
+    temp->next = NULL;
+
+    if (front == NULL)
+        front = rear = temp;
+    else {
+        rear->next = temp;
+        rear = temp;
+    }
+}
+int stack_linkedList::dequeue() {
+    linkedlist *temp;
+    int ele;
+    if (front == NULL)
+        std::cout << "\nStack is empty";
+    else {
+        temp = front;
+        ele = temp->data;
+        if (front == rear)  // if length of queue is 1;
+            rear = rear->next;
+        front = front->next;
+        delete (temp);
+    }
+    return ele;
+}
+void stack_linkedList::display() {
+    if (front == NULL)
+        std::cout << "\nStack is empty";
+
+    else {
+        linkedlist *temp;
+        temp = front;
+        while (temp != NULL) {
+            std::cout << temp->data << " ";
+            temp = temp->next;
+        }
+    }
+}
+
+int main() {
+    int op, data;
+    stack_linkedList ob;
+    std::cout << "\n1. enqueue(Insertion) ";
+    std::cout << "\n2. dequeue(Deletion)";
+    std::cout << "\n3. Display";
+    std::cout << "\n4. Exit";
+
+    while (1) {
+        std::cout << "\nEnter your choice ";
+        std::cin >> op;
+        if (op == 1) {
+            std::cout << "Enter data ";
+            std::cin >> data;
+            ob.enqueue(data);
+        } else if (op == 2)
+            data = ob.dequeue();
+        else if (op == 3)
+            ob.display();
+        else if (op == 4)
+            exit(0);
+        else
+            std::cout << "\nWrong choice ";
+    }
+    return 0;
+}