DS1

#include <stdio.h>
#define STACK_SIZE 5

struct stackElement
{
    int value;
    struct stackElement* prev;
    struct stackElement* next;
};

struct stackElement* pushStack(struct stackElement* stackPointer, int value) {
    if (stackPointer == NULL) {
        stackPointer = (struct stackElement*) malloc(sizeof(struct stackElement));
        stackPointer->prev = NULL;
        stackPointer->next = NULL;
    }
    else {
        struct stackElement* newElement;
        newElement = (struct stackElement*) malloc(sizeof(struct stackElement));
        stackPointer->next = newElement;
        newElement->prev = stackPointer;
        newElement->next = NULL;
        stackPointer = newElement;
    }

    stackPointer->value = value;
    return stackPointer;
}

struct stackElement* popStack(struct stackElement* stackPointer, int* value) {
    if (stackPointer->prev == NULL) {
        *value = stackPointer->value;
        free(stackPointer);
        stackPointer = NULL;
    }
    else {
        *value = stackPointer->value;
        stackPointer = stackPointer->prev;
        free(stackPointer->next);
        stackPointer->next = NULL;
    }
    return stackPointer;
}

void printStack(struct stackElement* stackPointer) {
    int counter = 0;
    while (stackPointer != NULL) {
        printf("Value[%d]: %d\n", counter, stackPointer->value);
        stackPointer = stackPointer->prev;
        counter++;
    }
}

int main() {
    puts("Source stack:");
    struct stackElement* stack = NULL;
    struct stackElement* posStack = NULL;
    struct stackElement* negStack = NULL;

    for (int i = 0; i < STACK_SIZE; i++) {
        int temp = 0;
        printf("Enter value: ");
        scanf_s("%d", &temp);
        fseek(stdin, 0, SEEK_SET);
        stack = pushStack(stack, temp);
    }

    for (int i = 0; i < STACK_SIZE; i++) {
        int temp = 0;
        stack = popStack(stack, &temp);
        if (temp < 0) negStack = pushStack(negStack, temp);
        if (temp > 0) posStack = pushStack(posStack, temp);
    }

    puts("");

    puts("Positive stack:");
    printStack(posStack); puts("");

    puts("Negative stack:");
    printStack(negStack); puts("");
}