二叉搜索树，常量 NULL return

Question

我用二叉树写了一个电话簿搜索。代码中的所有内容都运行良好，但系统提示我输入要搜索的号码时除外。然后search_phonebook函数return默认为NULL。我无法破解它是什么。

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

#define MAX_NUM 15
#define MAX_NAME 50

typedef struct node {
    char *name_and_lastname;    
    char *phone;   
    struct node *left;
    struct node *right;
} Node;


Node* make_node(char *name, char* phone){

    Node *new = (Node *) malloc(sizeof(Node));

    if (new == NULL) 
      return NULL;


    new->name_and_lastname = (char*)malloc((strlen(name)+1)*sizeof(char));
    if( new->name_and_lastname == NULL) {
        free(new);
        return NULL; 
    }


    new->phone = (char*)malloc((strlen(phone)+1)*sizeof(char));
    if( new->phone == NULL) {
        free(new);
        return NULL; 
    }

    strcpy(new->name_and_lastname, name);
    strcpy(new->phone, phone);
    new->left = NULL;
    new->right = NULL;


    return new;
}


void free_tree(Node ** root_adress) {

    if (*root_adress == NULL)
        return ; 

    free_tree(&(*root_adress)->left);
    free_tree(&(*root_adress)->right);

    free((*root_adress)->name_and_lastname);
    free(*root_adress);
    *root_adress =  NULL;
}



void check_allocation(Node* new) {
    if( new == NULL) {
        fprintf(stderr, "Malloc error for new node!\n");
        exit(EXIT_FAILURE);
    }
}



void add_node(Node ** root_adress, char *name, char* phone) {

    if( *root_adress == NULL){ 
       Node* new = make_node(name, phone);
        check_allocation( new);
        *root_adress = new;  
        return;
    }

    if (strcmp((*root_adress)->name_and_lastname, name) < 0)
        add_node(&(*root_adress)->right, name, phone);
    else 
        if (strcmp((*root_adress)->name_and_lastname, name) > 0)
            add_node(&(*root_adress)->left, name, phone);
}



void print_phonebook(Node * root) {   
    if (root == NULL)
        return;

    print_phonebook(root->left);
    printf("%s: %s\n", root->name_and_lastname, root->phone);
    print_phonebook(root->right);
}



int read_contact(FILE * f, char *name , char* phone) {
    int c;
    int i = 0;
    int j=0;

while( (c=fgetc(f)) != EOF ) {

if ( !isdigit(c) && !ispunct(c) && c != '\n')
name[i++]=c;


if ( !isspace(c) && !isalpha(c))
phone[j++]=c;
else if ( j>0 )
break;

}


name[i]='[=11=]';

phone[j]='[=11=]';    

if ( i==0 && j==0)
return EOF;
else
return 0;

}

Node* search_phonebook(Node* root, char* name) {

    if(root == NULL)
        return NULL;

    if(strcmp(root->name_and_lastname,name) ==0 )
        return root;

    if( strcmp(root->name_and_lastname,name) > 0)
        return search_phonebook(root->left, name);
    else 
        return search_phonebook(root->right, name);
}

int main(int argc, char **argv) {
    Node *root = NULL, *x;
    FILE *f=NULL;
    char name[MAX_NAME];
    char phone[MAX_NUM];
    char c;
    int i;


    if (argc < 2) {
        fprintf(stderr, "Add the .txt file in the command line!\n");
        exit(0);
    }


    if ((f = fopen(argv[1], "r")) == NULL) {
        fprintf(stderr, "fopen() error\n");
        exit(1);
    }

    while (read_contact(f, name, phone) != EOF) 
        add_node(&root, name, phone);


    fclose(f);


    print_phonebook(root);

    printf("Whose number are we looking for?");
    i=0;


    while ((c=getchar())!='\n') name
    [i++] =c ;


    name[i]='[=11=]';   

    x = search_phonebook(root,name);
    if(x == NULL)
        printf("Not in the phonebook!\n");
    else 
        printf("%s %s \n", x->name_and_lastname, x->phone);


    free_tree(&root);

    return 0;
}

电话簿是这样的：

Peter Peterson 84/246-654
Mark Ronson 16/245-964
Steve Rock 174/53-247

Answer 1

if ( !isdigit(c) && !ispunct(c) && c != '\n')
    name[i++]=c;

这将包括名称末尾的空格。所以你需要搜索 "Mark Ronson " （注意末尾的空格）。或者更好的是，您应该编写代码以不在名称中包含最后一个空格。

顺便说一句，关于调试的一般提示。如果您使用调试器或只是在代码中添加了一些调试 printfs 来检查数据的有效性，您很容易发现这个问题。

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