Question

I'm trying to implement a queue using an array within C++. I cannot for the life of me figure out why some of my methods are not working properly. My exists method does not find a value that's in the queue and my duplicate method is duplicating the rear of my queue instead of the front. The duplicate method should take whatever is at the front of the queue (given it's not empty or full), copy that value, and put it at the front of the queue. Mine will take the rear value, copy it, and put it one position from the rear. In addition, the Enqueue method is not properly inserting values.

Here's my code, I'm not 100% sure what really works well or what doesnt.

#include <iostream>
#include "queue.h"

using namespace std;

static int nums[10];
int front = 0, rear = 0, sizeOfArray = 0;
int initialCapacity = 10;

int Enqueue(int num) {
   if (sizeOfArray == initialCapacity) {
       return -58;
   }
       for (int i = 0; i < initialCapacity; i++) {
           if (nums[i] == num) {
               return -62;
           }
           else {
               nums[rear] = num;
               rear = (rear + 1);
               sizeOfArray++;
               return 0;
           }  
   }
}

int Dequeue(int& num) {
   if (sizeOfArray == 0) {
       return -64;
   }
   front = (front + 1);
   sizeOfArray--;
   return 0;
}

int isEmpty() {
   if (sizeOfArray == 0) {
       return 1;
   }
   else {
       return 0;
   }
}

int Exists(int num) {
   for (int i = 0; i < sizeOfArray; i++) {
       int index = (front + i);
       if (nums[index] == num) {
           return 1;
       }
       else {
           return 0;
       }
      
   }
   return 0;
}

void Clear(void) {
   front = rear = sizeOfArray = 0;
}

void Print(void) {
   for (int i = 0; i < sizeOfArray; i++) {
       cout << nums[i] << " ";

   }
   cout << endl;
}

int Duplicate(void) {
   if (sizeOfArray == 0) {
       return -78;
   }
   if (sizeOfArray == initialCapacity) {
       return -81;
   }
   int dupeNum;
   dupeNum = nums[front];

   nums[front + 1] = dupeNum;
   sizeOfArray++;
   return 0;
}

Whenever I do the following methods in a test driver: Enqueue 4 Enqueue 5 Exists 5 Duplicate Print

I get this output:

Test 1 0 - 0 indicates success

Test 2 0 - 0 indicates success

Test 3 0 - 0 indicates a failure

Test 4 0 - indicates a success

4 4 0

Answer 1

In case of any queries, please revert back. I have fixed the enqueue and Duplicate Methods.

#include <iostream>
// #include "queue.h"

using namespace std;

/* Made Some Changes Here..... */
static int nums[10];
int front = 0, sizeOfArray = 0;
int initialCapacity = 10;
//Keep rear as start capacity - 1 for proper function of enqueue
int rear=initialCapacity-1;

int Enqueue(int num) {
if (sizeOfArray == initialCapacity) {
return -58;
}
   /* As we kept rear as start capacity - 1, we dont need loop */
   /* Increment rear.If it goes above capacity but queue is not full, we do modulus of intitialCapacity */
           rear = (rear + 1)%initialCapacity;
nums[rear] = num;
sizeOfArray++;
return 0;


}

int Dequeue(int num) {
if (sizeOfArray == 0) {
return -64;
}
front = (front + 1)%initialCapacity;
sizeOfArray--;
return 0;
}

int isEmpty() {
if (sizeOfArray == 0) {
return 1;
}
else {
return 0;
}
}

int Exists(int num) {
for (int i = 0; i < sizeOfArray; i++) {
int index = (front + i);
if (nums[index] == num) {
return 1;
}
else {
return 0;
}
  
}
return 0;
}

void Clear(void) {
front = rear = sizeOfArray = 0;
}

void Print(void) {
for (int i = 0; i < 10; i++) {
cout << nums[i] << " ";

}
cout << endl;
}

//The Logic was Wrong.
int Duplicate(void) {
if (sizeOfArray == 0) {
return -78;
}
if (sizeOfArray == initialCapacity) {
return -81;
}
int dupeNum;
dupeNum = nums[front];
//first increase size
sizeOfArray++;
//put start of queue ie. front as temp
int temp=nums[front],x,i=front;
//now loop from front till size of queueu
while(i<sizeOfArray){
   //Shift All Numbers to the right.
   x=nums[i];
   nums[i]=temp;
   temp=x;
   i++;
}
   //You will see that it generates duplicate
return 0;
}

int main(){
int a = Enqueue(47);
int b = Enqueue(97);
int c = Enqueue(60);
Print();
Duplicate();
Print();
return 0;
}