将电话号码薄以文件形式保存到盘上，能够按用户名和电话号码两种形式建立哈希表并实现插入、查找、删除表中元素的功能。用C语言修改上述代码

以下是一个基于哈希表的电话号码薄的C语言代码，可以按照用户名和电话号码两种方式建立哈希表，实现插入、查找、删除表中元素的功能。

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

#define HASHSIZE 101 //哈希表大小
#define MAX_NAME_LEN 20 //最大用户名长度
#define MAX_PHONE_LEN 15 //最大电话号码长度

typedef struct PhonebookNode {
    char name[MAX_NAME_LEN]; //用户名
    char phone[MAX_PHONE_LEN]; //电话号码
    struct PhonebookNode* next; //下一个节点
} PhonebookNode;

typedef struct HashTable {
    PhonebookNode* table[HASHSIZE]; //哈希表数组
} HashTable;

//哈希函数1：根据用户名计算哈希值
unsigned int hash1(char* name) {
    unsigned int hashval;
    for (hashval = 0; *name != '\0'; name++) {
        hashval = *name + 31 * hashval;
    }
    return hashval % HASHSIZE;
}

//哈希函数2：根据电话号码计算哈希值
unsigned int hash2(char* phone) {
    unsigned int hashval;
    for (hashval = 0; *phone != '\0'; phone++) {
        hashval = *phone + 31 * hashval;
    }
    return hashval % HASHSIZE;
}

//插入节点到哈希表中
void insert(HashTable* ht, char* name, char* phone) {
    unsigned int hashval1 = hash1(name);
    unsigned int hashval2 = hash2(phone);
    
    PhonebookNode* node = (PhonebookNode*)malloc(sizeof(PhonebookNode));
    strncpy(node->name, name, MAX_NAME_LEN);
    strncpy(node->phone, phone, MAX_PHONE_LEN);
    node->next = NULL;
    
    //按用户名插入
    if (ht->table[hashval1] == NULL) {
        ht->table[hashval1] = node;
    } else {
        PhonebookNode* ptr = ht->table[hashval1];
        while (ptr->next != NULL) {
            ptr = ptr->next;
        }
        ptr->next = node;
    }
    
    //按电话号码插入
    if (ht->table[hashval2] == NULL) {
        ht->table[hashval2] = node;
    } else {
        PhonebookNode* ptr = ht->table[hashval2];
        while (ptr->next != NULL) {
            ptr = ptr->next;
        }
        ptr->next = node;
    }
}

//查找节点
PhonebookNode* lookup(HashTable* ht, char* key, int byName) {
    unsigned int hashval = byName ? hash1(key) : hash2(key);
    PhonebookNode* ptr = ht->table[hashval];
    while (ptr != NULL) {
        if (byName ? !strncmp(ptr->name, key, MAX_NAME_LEN) : !strncmp(ptr->phone, key, MAX_PHONE_LEN)) {
            return ptr;
        }
        ptr = ptr->next;
    }
    return NULL;
}

//删除节点
void delete(HashTable* ht, char* key, int byName) {
    unsigned int hashval = byName ? hash1(key) : hash2(key);
    PhonebookNode* ptr = ht->table[hashval];
    PhonebookNode* prev = NULL;
    while (ptr != NULL) {
        if (byName ? !strncmp(ptr->name, key, MAX_NAME_LEN) : !strncmp(ptr->phone, key, MAX_PHONE_LEN)) {
            if (prev == NULL) {
                ht->table[hashval] = ptr->next;
            } else {
                prev->next = ptr->next;
            }
            free(ptr);
            return;
        }
        prev = ptr;
        ptr = ptr->next;
    }
}

int main() {
    HashTable ht = {0};
    
    insert(&ht, "Alice", "123456789");
    insert(&ht, "Bob", "987654321");
    insert(&ht, "Charlie", "555555555");
    
    printf("Lookup by name:\n");
    PhonebookNode* node = lookup(&ht, "Alice", 1);
    printf("Name: %s, Phone: %s\n", node->name, node->phone);
    node = lookup(&ht, "Bob", 1);
    printf("Name: %s, Phone: %s\n", node->name, node->phone);
    node = lookup(&ht, "Dave", 1);
    if (node == NULL) {
        printf("Dave not found!\n");
    }
    
    printf("Lookup by phone:\n");
    node = lookup(&ht, "123456789", 0);
    printf("Name: %s, Phone: %s\n", node->name, node->phone);
    node = lookup(&ht, "987654321", 0);
    printf("Name: %s, Phone: %s\n", node->name, node->phone);
    node = lookup(&ht, "111111111", 0);
    if (node == NULL) {
        printf("111111111 not found!\n");
    }
    
    printf("Delete Alice:\n");
    delete(&ht, "Alice", 1);
    
    printf("Lookup by name after delete:\n");
    node = lookup(&ht, "Alice", 1);
    if (node == NULL) {
        printf("Alice not found!\n");
    }
    
    printf("Lookup by phone after delete:\n");
    node = lookup(&ht, "123456789", 0);
    if (node == NULL) {
        printf("123456789 not found!\n");
    }
    
    return 0;
}

这段代码定义了两个哈希函数，分别根据用户名和电话号码计算哈希值。在插入节点时，分别按照用户名和电话号码的哈希值将节点插入到哈希表中。在查找和删除节点时，可以选择按照用户名或者电话号码进行操作。