C语言链表的问题：依次输入三个数字但是只输出一个并且Node*p指针不会指向下一个结点而是指向NULL

Question

这是个简易链表，我依次输入1 2 3但是最后只会输出1，并且输出1后，Node* p就会指向NULL，我不理解为什么会这样，请各位帮我看看

#include<stdio.h>
#include<stdlib.h> 
typedef struct _node {
    int value;
    struct _node* next;
}Node;
typedef struct {
    Node* head;
}List;
void add(List* plist, int number);
int main(int argc, char* argv[])
{
    List list;
    list.head=NULL;
    int number;
    do {
        scanf("%d", &number);
        add(&list, number);
    } while (number != -1);
    Node*p;
    for(p=list.head;p;p=p->next){
        printf("p=%d\n",p->value);
    }
    return 0;
}
void add(List* plist, int number) 
{
    if (number != -1) 
    {
        Node* p = (Node*)malloc(sizeof(Node));
        p->value = number;
        p->next=NULL;
        Node* last = plist->head;
        if (last)
         {
            while (last->next) {
             last = last->next;
             last->next = p;
            }
        }else {
             plist->head = p;
             }
    }
}

Answer 1

你的第33到36行，判断头指针存不存在，只有第一次添加链表时将1加了上去，后面的2，3由于last存在，所以进入第一个if(last),在判断while时，last->next肯定不存在。建议你把第38行放到while循环外面。

#include<stdio.h>
#include<stdlib.h> 
typedef struct _node {
    int value;
    struct _node* next;
}Node;
typedef struct {
    Node* head;
}List;
void add(List* plist, int number);
int main(int argc, char* argv[])
{
    List list;
    list.head=NULL;
    int number;
    do {
        scanf("%d", &number);
        add(&list, number);
    } while (number != -1);
    Node*p;
    for(p=list.head;p;p=p->next){
        printf("p=%d\n",p->value);
    }
while (p)
    {
        Node *q = p;
        p = p->next;
        free(q);
    }

    return 0;
}
void add(List* plist, int number) 
{
    if (number != -1) 
    {
        Node* p = (Node*)malloc(sizeof(Node));
        p->value = number;
        p->next=NULL;
        Node* last = plist->head;
        if (last)
         {
            while (last->next) {
             last = last->next;}
             last->next = p；
        }else {
             plist->head = p;
             }
    }
}