Created: 2023-09-29 18:50
Status: #concept
Subject: Programming
Tags: C Data Structure Queue

Stack

Implementations

#define MAX 10

• Arrays

struct Stack
{
  char data[MAX];
  int top;
};

• Linked List with Pointer to Pointer

typedef struct node {
  char data;
  struct node *next;
} *Node;

struct Stack {
  Node topPtr;
  int length;
};

Common Operations

/**
 * @brief Adds the specified element to the top of the stack.
 * 
 * @param s a pointer to the Stack object (struct Stack *)
 * @param ch the element to add to the stack
 */
void push(Stack s, char elem) {
  // checks if there is available space to insert
  if (s->length < MAX) {
    Node newNode = (Node)malloc(sizeof(struct node));

    if (newNode != NULL) {
      newNode->data = elem;
      // set the link of newNode to the topPtr
      newNode->next = s->topPtr;
      // set topPtr to newNode
      s->topPtr = newNode;
    }

    s->length++;
  }
}

/**
 * @brief Removes the element at the top of the stack.
 * 
 * @param s a pointer to the Stack object (struct Stack *)
 */
void pop(Stack s) {
  // checks if there is a node to delete
  if (s->topPtr != NULL) {
    // initialize temp to topPtr
    Node temp = s->topPtr;
    // set topPtr to topPtr link
    s->topPtr = s->topPtr->next;
    // dealloctes temp
    free(temp);
    
    s->length--;
  }
}

/**
 * @brief Returns the element at the top of the stack, otherwise ('\0') if the stack is empty.
 * 
 * @param s a pointer to the Stack object (struct Stack *)
 * @return char 
 */
char top(Stack s) {
  return (s->topPtr == NULL) ? '\0' : s->topPtr->data;
}

References