Queue using linkedlist

 struct Queue
 {
        int Data;
        struct Queue* next;
 }*rear, *front;

void enqueue (int value)
{
    if (rear == NULL)
    {
        rear = (struct Queue *) malloc(sizeof(struct Queue));
        rear->next = NULL;
        rear->Data = value;
        front = rear;
    }
    else
    {
        temp = (struct Queue *)malloc(sizeof(struct Queue));
        rear->next = temp;
        temp->Data = data;
        temp->next = NULL;
 
        rear = temp;
    }
}

void dequeue()
{
    front1 = front;
 
    if (front1 == NULL)
    {
        printf(" Error: Trying to display elements from empty queue");
        return;
    }
    else
        if (front1->next != NULL)
        {
            printf("Dequed value : %d", front1->Data);
            front1 = front1->next;
            free(front);
            front = front1;
        }
        else
        {
            printf("Dequed value : %d", front->Data);
            free(front);
            front = NULL;
            rear = NULL;
        }
}

void display()
{
     struct Node *var = rear;
     if(var == NULL)
        printf("\nQueue is Empty");
     else
     {
        while(var!=NULL)
        {
           printf("%d",var->Data);
           var=var->next;
         }
     }      
}

Queue using array

#define MAX 10
int queue[MAX], front=-1, rear=-1;

void enqueue (int num)
{
  if(front == 0 && rear == MAX-1)
    printf("Queue OverFlow Occured");
  
  else if(front == -1 && rear == -1)
  {
      front = rear = 0;
      queue[rear] = num;
  }

  else if(rear == MAX-1 && front != 0)
  {
    rear = 0;
    queue[rear] = num;
  }
  else
  {
      rear++;
      queue[rear] = num;
  }
}

void dequeue()
{
  if(front == -1)
  {
      printf("Underflow");
      return
  }
  int element = queue[front];
  if(front == rear)
     front = rear = -1;
  if(front == MAX-1)
     front = 0;
  else
     front++;
    
   printf("The deleted element is: %d", element);
}

Stack using Linked List

struct Stack
{
    int Data;
    struct Stack *next;
}*top;

void popStack()
{
    struct Stack *temp = top;
    if(temp == NULL)
        printf("\nStack Empty")
    else{
        top = top->next;
        free(temp);
    }
}

void pushStack(int value)
{
    struct Stack *temp;
    temp=(struct Stack *)malloc(sizeof(Stack Node));
    temp->Data=value;
    if (top == NULL)
    {
         top=temp;
         top->next=NULL;
    }
    else
    {
        temp->next=top;
        top=temp;
    }
}

void display()
{
     struct Stack *var=top;
     if(var == NULL)
         printf("Stack is Empty");
     else
     { 
          while(var!=NULL) {
               printf("%d \n",var->Data);
               var=var->next;
          } 
     }

}

Stack using array

#define size 10
struct stack {
   int s[size];
   int top;
} st;
 
int stfull() {
   if (st.top >= size - 1)
      return 1;
   else
      return 0;
}
 
void push(int item) {
   st.s[st.top++] = item;
}
 
int stempty() {
   if (st.top == -1)
      return 1;
   else
      return 0;
}
 
int pop() {
   int item;
   item = st.s[st.top];
   st.top--;
   return (item);
}
 
void display() {
   int i;
   if (stempty())
      printf("\nStack Is Empty!");
   else {
      for (i = st.top; i >= 0; i--)
         printf("\n %d", st.s[i]);
   }
}