在链表中搜索字符串 C

Question

我在 C 中搜索链表时遇到问题。我设法搜索并找到一个整数条目，但在字符串（名字和姓氏）方面遇到问题。基本上，有三个功能可以按名字、姓氏和号码在电话簿中搜索条目。是否也可以在找到搜索时显示该条目？请在下面找到代码。感谢您的帮助。

struct node { 
    char firstname[32]; 
    char lastname[32]; 
    int *number; 
    struct node *next; 
}*head; 

struct node *start=NULL; 

struct node *getnode() { 
    return((struct node *)malloc(sizeof(struct node)));
}

void insert() { 
    struct node *temp,*nn; 
    nn=getnode(); 
    temp=start; 
    while(temp->next!=NULL) 
    { 
        temp=temp->next; 
    } 
    printf("Enter First name:\n"); 
    scanf("%s",&nn->firstname); 
    printf("Enter Last name:\n"); 
    scanf("%s",&nn->lastname); 
    printf("Enter number:\n"); 
    scanf("%d",&nn->number); 
    temp->next=nn; 
    nn->next=NULL; 
    display(start);
} 


struct node *create() {
    struct node *temp,*nn; 
    if(start!=NULL) insert(); 
    else { 
        nn=getnode(); 
        start=nn; 
        temp=start; 
        printf("Enter First name:\n"); 
        scanf("%s",&nn->firstname); 
        printf("Enter Last name:\n"); 
        scanf("%s",&nn->lastname); 
        printf("Enter number:\n"); 
        scanf("%d",&nn->number); 
        nn->next=NULL;
    }
} 

void searchByFirstName() { 
    char *f;
    struct node* temp, *nn;
    temp = start;
    while (temp != NULL){
        printf("Enter First Name to be searched:\n");  scanf("%s",&f);
        printf("%s", &f);
        if (temp -> firstname == f){
            printf ("\n Record Found!\n");
            temp = temp -> next;
        }else{
            printf ("\n Record not found\n");
        } 
    }
} 

void searchByLastName() { 
    char *f;
    struct node* temp, *nn;
    temp = start;
    if (temp != NULL){
        printf("Enter Last Name to be searched:\n");  scanf("%s",&f);
        printf("%s", &f);
        if (temp -> lastname == f){
            printf ("\n Record Found!\n");
            temp = temp -> next;
        }else{
            printf ("\n Record not found\n");
        } 
    }
}

void searchByNumber() { 
    int *l;
    struct node* temp, *nn;
    temp = start;
    if (temp != NULL){
        printf("Enter Number to be searched:\n");  scanf("%d",&l);
        if (temp -> number == l){
            printf ("\n Record Found!\n");
            temp = temp -> next;
        }else{
            printf ("\n Record not found\n");
        } 
    }
}

Answer 1

在 C 中，您不能只使用运算符 == 比较两个字符串（也称为 char *）。在 C 中处理字符串时，可以使用标准函数 (#include )，例如：

strcmp(temp->lastname, f) // returns 0 in case of a perfect match

Answer 2

第 2 次编辑：添加了 Pretty 函数（最后一节）- 可以修改打印消息的示例。

编辑：在 searchByNumber2() 中添加了free(l)，修复了内存泄漏

对于你要的东西：

void searchByLastName() { 
    char f = char[32];
    struct node* temp, *nn;
    temp = start;

    printf("Enter Last Name to be searched:\n");  scanf("%s",f);
    printf("%s", f);
    while (temp != NULL){//!we search through whole list
        
        if (strcmp(temp -> lastname, f) == 0) {
            printf ("\n Record Found!\n");
            temp = temp -> next;
        }else{
            printf ("\n Record not found\n");
/*!you probably wanna pull this printf for after the loop;
I would either add bool Found and add if after the loop
or after the loop always print "search finished" or sth */


        } 
    }
}

还有两个版本的数字固定搜索（第二个以int *l为例；第一个使用int l，更简洁）

void searchByNumber() { 
    int l;
    struct node* temp, *nn;
    temp = start;
    printf("Enter Number to be searched:\n");  scanf("%d",&l);//&l is address of the int l
    while (temp != NULL){
        if (*(temp -> number) == l){//notice: temp->number is a pointer to int, not an int itself, l is an int here
            printf ("\n Record Found!\n");
            temp = temp -> next;
        }else{
            printf ("\n Record not found\n");
        } 
    }
}


void searchByNumber2() { 
    int *l = malloc(sizeof int);
    struct node* temp, *nn;
    temp = start;
    printf("Enter Number to be searched:\n");  scanf("%d",l);
    while (temp != NULL){
        if (*(temp -> number) == *l){//we want to compare int values, not their adresses, both temp->number and l are pointers here
            printf ("\n Record Found!\n");
            temp = temp -> next;
        }else{
            printf ("\n Record not found\n");
        } 
    }
free(l);
}

上次编辑

注意：此版本的 searchByLastNamePretty 会打印姓氏出现次数的 Found 消息，并在搜索后打印 Finished 消息。 另一方面，searchByNumberPretty 打印一条 Found 消息或一条 Not-Found 消息（始终只有一条消息；如果该数字出现很多则无关紧要）。

将它们用作您可以做什么的示例。分析bool Found的使用情况。

void searchByLastNamePretty() { 
    char f = char[32];
    struct node* temp, *nn;
    temp = start;

    printf("Enter Last Name to be searched:\n");  scanf("%s",f);
    printf("%s\n", f);  //better practice, to end printf with \n to flush it
    while (temp != NULL){//!we search through whole list
        
        if (strcmp(temp -> lastname, f) == 0) {
            printf ("Record Found!\n");
            temp = temp -> next;
        }
        printf("Search finished\n");
    }
}


void searchByNumberPretty() { 
    int l;
    struct node* temp, *nn;
    temp = start;
    printf("Enter Number to be searched:\n");
    scanf("%d",&l);//&l is address of the int l
    bool found = false;
    while (temp != NULL && !found){//!we search till the first occurence
        if (*(temp -> number) == l){//note: (temp->number) is a pointer to int, not an int
            found = true;
            temp = temp -> next;
        }
    }

    if (found) {
        printf("Record Found!\n");
    }
    else {
        printf("Record not found\n");
    }
}