【发布时间】：2015-11-24 21:59:25
【问题描述】：
这个程序应该创建一个排序列表并按名字和姓氏对每个用户进行排序。我似乎无法弄清楚如何正确地对名称进行排序。
我只有 append_to_list 函数有问题，其他函数都可以正常工作。
当我第一次开始输入姓名时：
user ID: Last Name: First Name:
3 Alex Alex
2 Jones Alex
1 andrew john
在我输入一个应该在两个名称之间排序的名称之前，它的排序很好 当我输入名字 Andrew, Alex 时，就会发生这种情况。
user ID: Last Name: First Name:
4 Andrew Alex
3 Alex Alex
2 Jones Alex
1 andrew john
但是安德鲁，亚历克斯应该在用户 2 和 3 之间
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "user.h"
#include "readline.h"
// function append_to_list takes user input from user, id, name and puts it to the end of the list
// as well as sorts each name alphabetically
struct user *append_to_list(struct user *family)
{
struct user *cur, *prev, *new_node;
// generate memory
new_node = malloc(sizeof(struct user));
if (new_node == NULL) {
printf("malloc failed in append\n");
return family;
}
printf("Enter user ID: \n");
scanf("%d", &new_node->number);
printf("Enter user last name: \n");
read_line(new_node->last_name,NAME_LEN);
printf("Enter user first name: \n");
read_line(new_node->first_name,NAME_LEN);
for( cur=family; cur != NULL; cur = cur->next) {
if (new_node->number == cur->number) {
printf("user already exists: %s, %s\n",new_node->first_name, new_node->last_name);
free(new_node);
return family;
}
}
for (cur=family, prev = NULL; cur != NULL
&& (strcmp(new_node->first_name,cur->first_name) < 0)
&& (strcmp(new_node->last_name,cur->last_name) < 0);
prev = cur, cur = cur->next) {
if((strcmp(new_node->last_name,cur->last_name) < 0)) break;
if((strcmp(new_node->first_name,cur->first_name) == 0))
if((strcmp(new_node->first_name,cur->first_name) < 0)) break;
;
}
// use strcmp == 0 to see if name already exists
if (cur != NULL && (strcmp(new_node->first_name,cur->first_name) == 0)
&& (strcmp(new_node->last_name,cur->last_name)) == 0)
{
printf("user already exists: %s, %s\n",new_node->first_name, new_node->last_name);
free(new_node);
return family;
}
// append the linkedlist to the end
new_node->next = cur;
// check to see if the node is empty
if (prev == NULL) {
return new_node;
} else {
prev->next = new_node->next;
return family;
}
}
// function delete_from_list removes a user from the family
struct user* delete_from_list(struct user *family)
{
struct user *prev, *cur;
int id;
int not_found = 0;
printf("Enter user ID: \n");
scanf("%d", &id);
for (cur = family, prev = NULL; cur != NULL; prev = cur, cur = cur->next) {
if (id == cur->number) {
// if only one user on family
if (prev == NULL) {
family = cur->next;
// if user is in the middle of family
// connects prev node to cur node
} else {
prev->next = cur->next;
}
printf("user deleted: %s ,%s\n",cur->first_name, cur->last_name);
free(cur);
}
else
not_found = 1;
}
if (not_found == 1) {
printf("user not found\n");
}
return family;
}
// function find_user searches the family by ID and matches it with the users name
void find_user(struct user *family)
{
struct user *p = family;
int id;
int count = 0;
printf("Enter user ID: \n");
scanf("%d", &id);
// compares the family with the user entered ID
// if the ID is the same count set to 1
if (p != NULL) {
for (p = family; p != NULL; p = p->next) {
if (id == p->number) {
count = 1;
break;
}
}
}
// if count is 1 we know the function found that specific user
if ( count == 1) {
printf("user found: %s, %s\n", p->last_name, p->first_name);
} else {
printf("user not found");
}
}
// function printList prints the entire family
void printList(struct user *family)
{
struct user *p;
printf("user ID:\tLast Name:\tFirst Name:\n");
for (p = family; p != NULL; p = p->next) {
printf("%d\t\t%s\t\t%s\n", p->number, p->last_name, p->first_name);
}
}
// function clearList clears the entired linked list
void clearList(struct user *family)
{
struct user *p;
while (family != NULL) {
p = family;
family = family->next;
if (p != NULL) {
free(p);
}
}
}
【问题讨论】：
-
为什么在循环终止条件和
append_to_list()的循环体中都有名称比较？ -
无论如何，我认为终止条件和循环体中的比较 both 都是错误的。至少，相同姓氏的情况似乎在两个地方都处理不正确。
标签： c sorting linked-list strcmp