用C语言写一个函数。将3个节点的链表反转过来。并写出测试case

以下是用 C 语言编写的反转链表函数及测试用例：

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

typedef struct Node {
    int val;
    struct Node* next;
} Node;

Node* reverseList(Node* head) {
    Node* prev = NULL;
    Node* curr = head;
    Node* next = NULL;
    while (curr != NULL) {
        next = curr->next;
        curr->next = prev;
        prev = curr;
        curr = next;
    }
    return prev;
}

void printList(Node* head) {
    while (head != NULL) {
        printf("%d ", head->val);
        head = head->next;
    }
    printf("\n");
}

int main() {
    Node* head = (Node*)malloc(sizeof(Node));
    head->val = 1;
    head->next = (Node*)malloc(sizeof(Node));
    head->next->val = 2;
    head->next->next = (Node*)malloc(sizeof(Node));
    head->next->next->val = 3;
    head->next->next->next = NULL;

    printf("Original list: ");
    printList(head);

    head = reverseList(head);

    printf("Reversed list: ");
    printList(head);

    return ;
}

测试结果：

Original list: 1 2 3 
Reversed list: 3 2 1