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queue_ll.cpp
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queue_ll.cpp
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// Copyright 2019 Souvik Biswas
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
#include <iostream>
using namespace std;
/*
Declaring a structure called node
having two members:
1) data block
2) next block (which stores the address of the next node)
*/
struct node {
int data;
node *next;
};
/*
Declaring a class called Queue having:
two private member:
front
rear
three public member functions:
insert
delete
display
The top is set to NULL initially
*/
class Queue {
node *front, *rear;
public:
Queue(): front(NULL), rear(NULL) {}
void insert(int );
void del();
void display();
};
/*
ALGORITHM FOR INSERTING AN ELEMENT IN THE QUEUE:
1) IF AVAIL = NULL
WRITE Overflow
EXIT
2) NEW_NODE = AVAIL
3) AVAIL = AVAIL -> NEXT
4) NEW_NODE -> DATA = VALUE
5) NEW_NODE -> NEXT = NULL
6) IF REAR = NULL
REAR = NEW_NODE
FRONT = NEW_NODE
6) ELSE
REAR -> NEXT = NEW_NODE
REAR = NEW_NODE
7) EXIT
*/
void Queue :: insert(int value) {
node *new_node = new node;
new_node->data = value;
new_node->next = NULL;
if(rear == NULL) {
rear = new_node;
front = new_node;
}
else {
rear->next = new_node;
rear = new_node;
}
}
/*
ALGORITHM TO DELETE A NODE FROM QUEUE:
1) IF FRONT = NULL
WRITE Underflow
EXIT
2) PTR = FRONT;
3) FRONT = FRONT -> NEXT
4) DELETE PTR
5) EXIT
*/
void Queue :: del() {
// Checking if the queue is empty
if(front == NULL) {
cout<<"The Queue is empty !\n";
}
else {
// Storing the front node in ptr
node *ptr = front;
// Incrementing front
front = front->next;
// Printing the element to be deleted
cout<<"The deleted node is: "<<ptr->data<<endl;
// Delete the node
delete ptr;
}
// Solving the edge case #1:
// When the front becomes null, we have to set rear to null also
if(front == NULL) {
rear = NULL;
}
}
/*
ALGORITHM TO DISPLAY THE QUEUE:
1) IF FRONT = NULL
WRITE Underflow
EXIT
2) PTR = FRONT
3) WHILE PTR != NULL
PTR = PTR -> NEXT
4) EXIT
*/
void Queue :: display() {
if(front == NULL) {
cout<<"The Queue is empty !\n";
}
else {
node *ptr = front;
while(ptr != NULL) {
cout<<ptr->data<<" ";
ptr = ptr->next;
} cout<<endl;
}
}
// Main Function
int main() {
int option, value;
Queue q;
do {
cout<<"\n**** MENU ****\n"
<<"1. Insert\n"
<<"2. Delete\n"
<<"3. Display\n"
<<"4. Exit\n";
cout<<"Enter your option: ";
cin>>option;
switch(option) {
case 1: cout<<"Enter the value to be inserted: ";
cin>>value;
q.insert(value);
break;
case 2: q.del();
break;
case 3: q.display();
break;
case 4: break;
default: cout<<"Wrong option !\n";
break;
}
} while(option != 4);
if(option == 4) {
cout<< "\nTHANK YOU for using the program !\n"
<<"Have a good day.\n\n";
}
}