C 语言在线编译器

main.c

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StdinOptional input fed to the program on stdin - one line per line.2 linesAlice 30

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#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
    int value;
    struct Node* prev;
    struct Node* next;
} Node;

Node* head = NULL;
Node* tail = NULL;

Node* newNode(int value) {
    Node* n = calloc(1, sizeof(Node));
    n->value = value;
    return n;
}

void append(int value) {
    Node* node = newNode(value);
    if (tail == NULL) {
        head = tail = node;
        return;
    }
    node->prev = tail;  // link both directions
    tail->next = node;
    tail = node;
}

void prepend(int value) {
    Node* node = newNode(value);
    if (head == NULL) {
        head = tail = node;
        return;
    }
    node->next = head;
    head->prev = node;
    head = node;
}

void printForward(void) {
    for (Node* cur = head; cur != NULL; cur = cur->next) {
        printf("%d <-> ", cur->value);
    }
    printf("NULL\n");
}

void printBackward(void) {
    for (Node* cur = tail; cur != NULL; cur = cur->prev) {
        printf("%d <-> ", cur->value);
    }
    printf("NULL\n");
}

int main(void) {
    int values[] = {10, 20, 30};
    for (int i = 0; i < 3; i++) append(values[i]);
    prepend(5);
    printf("Forward:  ");
    printForward();
    printf("Backward: ");
    printBackward();
    return 0;
}