dailycodebase/day43/JavaScript/queueReversal.js at master · CodeToExpress/dailycodebase · GitHub

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/**
 * Queue reversal
 * @author MadhavBahl
 * @date 15/02/2019
 * Method
 * - Dequeue the elements from queue and keep pushing them in stack
 * - Pop the elements from stack and enqueue them in the original queue
 */

// Class declaration for queue data structure
classQueue{
constructor(size){
this.capacty=size;
this.data=[];
this.frontIndex=0;
this.rearIndex=0;
}

front(){
returndata[this.frontIndex];
}

rear(){
returndata[this.rearIndex-1];
}

enqueue(element){
if(this.rearIndex>=this.capacty){
console.log("Overflow!");
return-1;
}
this.data.unshift(element);
// console.log (element + ' added to the queue');
this.rearIndex++;
}

dequeue(element){
if(this.rearIndex===0){
console.log("Underflow!");
return-1;
}
// console.log (this.data[this.rearIndex -1] + ' has been removed from the queue');
this.rearIndex--;
returnthis.data.pop();
}

displayQueue(){
lettoBeDisplayed='-> ';
for(letelementofthis.data){
toBeDisplayed+=element+' -> ';
}
console.log(toBeDisplayed);
}
}

// Class declaration for stack data structure
classStack{
// constructor to initialize the stack and it's capacity
constructor(limit){
this.myStack=[];
this.top=limit;
}

// isEmpty method to check whether the stack is empty
isEmpty(){
if(this.myStack.length===0)returntrue;
elsereturnfalse;
}

// isFull method to check whether the stack is full
isFull(){
if(this.myStack.length===this.top)returntrue;
elsereturnfalse;
}

// push method to add a record to the stack
push(record){
if(!this.isFull()){
this.myStack.push(record);
}else{
console.log('Sorry! The Stack is full!');
}
}

// pop method to remove an element from the stack
pop(){
if(!this.isEmpty()){
returnthis.myStack.pop();
}else{
console.log('Sorry! The Stack is empty');
}
}

// peek method to view the top element
peek(){
console.log(`Current element is: ${this.myStack[this.myStack.length-1]}`);
}
}

constreverse=(myQueue)=>{
conststack=newStack(10);
letlen=myQueue.rearIndex;

for(leti=len;i>0;i--){
letcurrentElement=myQueue.dequeue();
stack.push(currentElement);
}

for(leti=0;i<len;i++){
letcurrentElement=stack.pop();
myQueue.enqueue(currentElement);
}
};

constmyQueue=newQueue(4);

myQueue.enqueue(1);
myQueue.enqueue(2);
myQueue.enqueue(3);
myQueue.enqueue(4);

console.log("\n/* ===== Displaying Initial Queue ===== */");
myQueue.displayQueue();

reverse(myQueue);

console.log("\n/* ===== Displaying Final Queue ===== */");
myQueue.displayQueue();