Sep 30, 2020
diff --git a/src/chapter05queues/DynamicArrayQueue.java b/src/chapter05queues/DynamicArrayQueue.java
 // Initializes the queue to use an array of given length.
 public DynamicArrayQueue (int cap){
 queueRep = new int [ cap];
 //Resetting the CAPACITY to current user provided cap value.
 CAPACITY = cap;
 size  = 0; front = 0; rear  = 0;
 }

 int length = size();
 int[] newQueue = new int[length<<1];  // or 2* length

 //copy items
 for(int i = front; i <= rear; i ++)
 newQueue[i-front] = queueRep[i%CAPACITY];
 //This loop wont work for circular case when our rear will be pointing to the same location as that of front , i.e
 // queue[5] = {1,2,3,4,5} , now our rear will be at (rear + 1) % CAPACITY
 // i.e 0 and loop condition will run only once.
 // for(int i = front; i <= rear; i ++)
 // newQueue[i-front] = queueRep[i%CAPACITY];

 // if front and  rear pointer are pointing at the exact same location i.e 0 , when only enqueue is done and not dequeue uptil capacity
        if(rear == 0){
            for(int i = 0 ; i < queueRep.length ; i++){
                newQueue[i] = queueRep[i];
            }
        }

       // if front and  rear pointer are pointing at the exact same location but not at 0 , i.e dequeue() is also performed in between.
        else{

            int j = 0, temp = front;
            //System.out.println("temp value : " + temp + " and rear " + rear);

            //we go only till one element before rear pointer , because there might be a issue of rear and front both pointer pointing at same location other than 0
            while(temp != rear - 1){
                newQueue[j] = queueRep[temp%CAPACITY];
                j++;
                temp = (temp+1) % CAPACITY;

            }

            newQueue[j] = queueRep[temp];

        }


 queueRep = newQueue;
 front = 0;
 rear = size-1;
 //if we go uptil size - 1 then we will be pointing the latest element entered in our queue and not the latest free slot to enter
 // the value
 //rear = size-1;
 //as size is incremented each time on enqueue and decremented each time at dequeue
 rear = size;
 CAPACITY *= 2;
 }

 result += "]";
 return result;
 }
 }
 }
Original file line number	Diff line number	Diff line change
Expand Up		@@ -33,6 +33,8 @@ public DynamicArrayQueue (){
		// Initializes the queue to use an array of given length.
		public DynamicArrayQueue (int cap){
		queueRep = new int [ cap];
		//Resetting the CAPACITY to current user provided cap value.
		CAPACITY = cap;
		size = 0; front = 0; rear = 0;
		}

Expand DownExpand Up		@@ -80,13 +82,45 @@ private void expand(){
		int length = size();
		int[] newQueue = new int[length<<1]; // or 2* length

		//copy items
		for(int i = front; i <= rear; i ++)
		newQueue[i-front] = queueRep[i%CAPACITY];
		//This loop wont work for circular case when our rear will be pointing to the same location as that of front , i.e
		// queue[5] = {1,2,3,4,5} , now our rear will be at (rear + 1) % CAPACITY
		// i.e 0 and loop condition will run only once.
		// for(int i = front; i <= rear; i ++)
		// newQueue[i-front] = queueRep[i%CAPACITY];

		// if front and rear pointer are pointing at the exact same location i.e 0 , when only enqueue is done and not dequeue uptil capacity
		if(rear == 0){
		for(int i = 0 ; i < queueRep.length ; i++){
		newQueue[i] = queueRep[i];
		}
		}

		// if front and rear pointer are pointing at the exact same location but not at 0 , i.e dequeue() is also performed in between.
		else{

		int j = 0, temp = front;
		//System.out.println("temp value : " + temp + " and rear " + rear);

		//we go only till one element before rear pointer , because there might be a issue of rear and front both pointer pointing at same location other than 0
		while(temp != rear - 1){
		newQueue[j] = queueRep[temp%CAPACITY];
		j++;
		temp = (temp+1) % CAPACITY;

		}

		newQueue[j] = queueRep[temp];

		}


		queueRep = newQueue;
		front = 0;
		rear = size-1;
		//if we go uptil size - 1 then we will be pointing the latest element entered in our queue and not the latest free slot to enter
		// the value
		//rear = size-1;
		//as size is incremented each time on enqueue and decremented each time at dequeue
		rear = size;
		CAPACITY *= 2;
		}

Expand DownExpand Up		@@ -117,4 +151,4 @@ public String toString(){
		result += "]";
		return result;
		}
		}
		}