Sequential Stack

A sequential stack uses an array with a top pointer to track the top element.

Stack Structure

typedef struct {
    int items[MAXLEN];
    int topIndex;
} SeqStack;

Initialize Stack

void CreateSeqStack(SeqStack *stack) {
    stack->topIndex = -1;
}

Check If Empty

int IsEmptySeq(SeqStack *stack) {
    return stack->topIndex == -1;
}

Check If Full

int IsFullSeq(SeqStack *stack) {
    return stack->topIndex == MAXLEN - 1;
}

Push Operation

int PushSeq(SeqStack *stack, elemType value) {
    if (IsFullSeq(stack)) {
        printf("Stack overflow\n");
        return 0;
    }
    stack->items[++stack->topIndex] = value;
    return 1;
}

Pop Operatoin

elemType PopSeq(SeqStack *stack) {
    if (IsEmptySeq(stack)) {
        printf("Stack underflow\n");
        exit(EXIT_FAILURE);
    }
    return stack->items[stack->topIndex--];
}

Peek Top Element

elemType PeekSeq(SeqStack *stack) {
    if (IsEmptySeq(stack)) {
        printf("Stack is empty\n");
        exit(EXIT_FAILURE);
    }
    return stack->items[stack->topIndex];
}

Linked Stack

A linked stack implements the stack using a singly linked list, where the head node represents the top of the stack.

Node Structure

typedef struct StackNode {
    elemType data;
    struct StackNode *next;
} StackNode;

typedef StackNode *LinkStack;

Check If Empty

int IsEmptyLink(LinkStack head) {
    return head == NULL;
}

Push Operation

LinkStack PushLink(LinkStack head, elemType val) {
    StackNode *node = (StackNode *)malloc(sizeof(StackNode));
    node->data = val;
    node->next = head;
    return node;
}

Pop Operation

LinkStack PopLink(LinkStack head, elemType *val) {
    if (IsEmptyLink(head)) {
        printf("Stack is empty\n");
        exit(EXIT_FAILURE);
    }
    *val = head->data;
    LinkStack temp = head;
    head = head->next;
    free(temp);
    return head;
}

Peek Top Element

elemType PeekLink(LinkStack head) {
    if (IsEmptyLink(head)) {
        printf("Stack is empty\n");
        exit(EXIT_FAILURE);
    }
    return head->data;
}

Comparision