Notes-TheAlgorithmDesignManual/DataStructures.org

Random Data Structures

• Stack
  • C

Stack

C

typedef struct Node {
    struct Node* next;
    /* void *data; */
    int data;
} Node;

typedef struct Stack {
    Node* top;
    int length;
} Stack;

/* void stack_create(void* data) { */
Stack *stack_create(int data) {
    Stack *stack = malloc(sizeof(Stack));
    Node *node = malloc(sizeof(Node));
    node->data = data;
    node->next = NULL;
    stack->top = node;
    stack->length = 1;
    return stack;
}

int stack_pop(Stack *stack) {
    Node *top = stack->top;
    Node *next = top->next;
    if (stack->length > 0 && next != NULL) {
        stack->top = next;
        stack->length--;
        int value = top->data;
        free(top);
        return value;
    } else {
        // A better API design would be to return a bool and the int as a pointer
        // Although once we switch away from int and use void pointers, might not be needed
        return -1;
    }
}

/* void stack_push(Stack *stack, void *data) { */
void stack_push(Stack *stack, int data) {
    Node *node = malloc(sizeof(Node));
    Node *top = stack->top;
    node->data = data;
    node->next = top;
    stack->top = node;
    stack->length++;
}

/* void* stack_peak(Stack *stack) { */
int stack_peak(Stack *stack) {
    return stack->top->data;
}

void stack_print(Stack *stack) {
    Node *current = stack->top;
    int i = 0;
    while (current != NULL) {
        printf("Stack at %d: %d\n", ++i, current->data);
        current = current->next;
    }
    printf("------------------\n");
}