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78.queue_circularQueue.cpp
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78.queue_circularQueue.cpp
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/**
* drawback of two pointer approach for creating queue is that
* _ _ 1 9 8 10
* ^ ^
* f r
*
* the two spaces before front are unused.
* basically, as we dequeue, the size of the queue gets smaller and smaller
* making out data structure inefficient
*
* Hence, we use something called as circular queue -
* 11 _ 1 9 8 10
* ^ ^
* r f
* here though, 1 space is left empty to satisfy both -
* r==f ->empty
* r%size==f-1 ->full
*/
#include<iostream>
using namespace std;
struct circular_q{
int size;
int front=0;
int rear=0;
int* arr;
};
void enqueue(circular_q &c,int x){
if((c.rear+1)%(c.size+1)==c.front){
cout<<"Queue is full.";
return;
}
c.rear = (c.rear+1)%(c.size+1);
c.arr[c.rear] = x;
}
int dequeue(circular_q &c){
int x=-1;
if(c.front==c.rear){
cout<<"queue is empty.";
return x;
}
c.front = (c.front+1)%(c.size+1);
x = c.arr[c.front];
return x;
}
void display(circular_q &c){
int i=c.front+1;
while(i!=c.rear+1){
cout<<c.arr[i++]<<" ";
}
cout<<endl;
}
int main(){
circular_q c;
cout<<"enter size of the queue: ";
cin>>c.size;
c.arr = new int[c.size+1];
dequeue(c);
cout<<endl;
for(int i=0;i<10;i++) enqueue(c,i);
display(c);
for(int i=0;i<3;i++) dequeue(c);
display(c);
}