找链表第K个节点的值

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

typedef struct ListNode {
    int value;
    struct ListNode *next;
} ListNode;

// 创建新节点
ListNode* createNode(int value) {
    ListNode* newNode = (ListNode*)malloc(sizeof(ListNode));
    newNode->value = value;
    newNode->next = NULL;
    return newNode;
}

// 查找倒数第k个节点
int findKthFromEnd(ListNode* head, int k) {
    ListNode *first = head, *second = head;

    // 移动first指针k步
    for (int i = 0; i < k; i++) {
        if (first == NULL) {
            return -1; // 表示未找到
        }
        first = first->next;
    }

    // 同时移动first和second指针
    while (first != NULL) {
        first = first->next;
        second = second->next;
    }

    return second->value; // 返回倒数第k个节点的值
}

int main() {
    int k;
    scanf("%d", &k);

    ListNode* head = NULL;
    ListNode* tail = NULL;
    int value;

    // 读取链表节点值
    while (scanf("%d", &value) == 1) {
        ListNode* newNode = createNode(value);
        if (head == NULL) {
            head = newNode;
            tail = newNode;
        } else {
            tail->next = newNode;
            tail = newNode;
        }
    }

    // 查找倒数第k个节点
    int result = findKthFromEnd(head, k);
    if (result == -1) {
        printf("Not Found\n");
    } else {
        printf("%d\n", result);
    }

    // 释放链表内存
    ListNode* current = head;
    while (current != NULL) {
        ListNode* temp = current;
        current = current->next;
        free(temp);
    }

    return 0;
}