C -链表在插入时删除值

Question

我正在尝试创建一个方法，让我在我喜欢的列表中插入一个新节点在选定的索引，当插入索引0或1时，它目前按预期工作，但当我试图插入任何索引>= 2时，列表中的第一个值正在丢失。知道为什么吗?

主要例子:

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

int main( void ) {
List list = new_list();

add(list, "Three");
add(list, "Two");
add(list, "Zero");
print_list(list);
printf("Inserting at 1 n");
insert_at(list, 1, "one")
print_list(list);
printf("Inserting at 2 n");
insert_at(list, 2, "inserted")
print_list(list);

头文件:

typedef struct Node{
char *value;
struct Node *next;
}Node;
typedef Node** List;
List new_list();
Node *new_node(char *value);
void add(List list,char *value);
int is_empty(List list);
void print_list(const List list);
int insert_at(List list,int index,char *value);

方法文件:

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

List new_list(){
List list = malloc(sizeof(List));
*list = NULL;
return list;
}
Node *new_node(char *value){
Node *node = malloc(sizeof(Node));
node->value = value;
node->next = NULL;
return node;
}
void add(List list,char *value){
if (*list == NULL){
*list = new_node(value);
}else {
Node *node = new_node(value);
node->next = *list;
*list = node;
}
}
int is_empty(List list){
if (*list == NULL){
return 1;
}   return 0;
}
void print_list(const List list){ 
printf("[");
Node *curr = *list;
if (curr == NULL){
printf("]n");
return;
} 
while (curr->next != NULL){
printf(""%s", ", curr->value );

curr = curr->next;
}
printf(""%s"", curr->value );
printf("]n");
}

int insert_at(List list,int index,char *value){

if ((index > 0 && is_empty(list) == 1) || index < 0){
return 0;
}
int i= 0;
if (index == 0){
add(list, value);
return 1;
}

while((*list) != NULL){
//advancing loop
i++; 
//checking if wanted index = lists index
if (i == index){
//creating new node
Node *node = new_node(value);
//updating next values;
node->next = (*list)->next;
(*list)->next = node;

return 1;
}
(*list) =(*list)->next;
}
return 0;
}

示例输出:

["Zero", "Two", "Three"]
Inserting at 1
["Zero", "One", "Two", "Three"]
Inserting at 2
["One", "INSERTED", "Two", "Three"]

Answer 1

在这个while循环中

while((*list) != NULL){
//advancing loop
i++; 
//checking if wanted index = lists index
if (i == index){
//creating new node
Node *node = new_node(value);
//updating next values;
node->next = (*list)->next;
(*list)->next = node;

return 1;
}
(*list) =(*list)->next;
}

声明

(*list) =(*list)->next;

覆盖指向头节点的指针，这至少会导致大量内存泄漏。

第二个函数参数应该是无符号整数类型，例如size_t。

函数new_list应该至少看起来像

List new_list(){
List list = malloc(sizeof( *list ));
*list = NULL;
return list;
}

一般来说，使用这样的typedef

是一种不好的方法

typedef Node** List;

它只会使代码的读者感到困惑。