如何通过ASCII向链表添加字母？

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

// 链表节点结构
typedef struct Node {
    char letter;
    struct Node* next;
} Node;

// 向链表添加字母
void addLetter(Node** head, char letter) {
    // 创建新节点
    Node* newNode = (Node*)malloc(sizeof(Node));
    newNode->letter = letter;
    newNode->next = NULL;
    
    // 如果链表为空，将新节点作为头节点
    if (*head == NULL) {
        *head = newNode;
        return;
    }
    
    // 遍历链表，找到合适的位置插入新节点
    Node* curr = *head;
    Node* prev = NULL;
    while (curr != NULL && curr->letter < letter) {
        prev = curr;
        curr = curr->next;
    }
    
    // 插入新节点
    if (prev == NULL) {
        newNode->next = *head;
        *head = newNode;
    } else {
        prev->next = newNode;
        newNode->next = curr;
    }
}

// 打印链表内容
void printList(Node* head) {
    Node* curr = head;
    while (curr != NULL) {
        printf("%c ", curr->letter);
        curr = curr->next;
    }
    printf("\n");
}

int main() {
    // 初始化链表头节点
    Node* head = NULL;
    
    // 添加字母到链表
    addLetter(&head, 'D');
    addLetter(&head, 'B');
    addLetter(&head, 'F');
    addLetter(&head, 'C');
    addLetter(&head, 'A');
    
    // 打印链表内容
    printList(head);
    
    return 0;
}