数据结构学习--创建链表

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#include "stdio.h"#include "stdlib.h"struct pass{int number;struct pass *next;};struct pass * createList(struct pass *head){int i = 0;struct pass *p1; /*要新加的节点*/struct pass *p2; /*尾节点*/head = NULL; /*头节点*/p1 = (struct pass*)malloc(sizeof(struct pass));p2 = p1;p1->next = NULL;for(i = 1; i<=10; ++i){if(p1 == NULL)return;p1->number = i;if(head == NULL){head = p1; //第一次循环时, 表是空的, 将p1设置为表头,此时head == p2 == p1;}else{p2->next = p1; //第二次开始, p1是新的节点, p2是表尾, 将表尾的next指向新节点}p2 = p1; //p2设为表尾p1 = (struct pass*)malloc(sizeof(struct pass));}p2->next = NULL; //没有这一句, p2将指向不明位置,导致下面的temp ==NULL的判断不起作用free(p1);     //一定要将将p1 free并且置为NULL, 否则指针变成"野指针", "野指针"指程序不再使用的指针,   //程序员无法控制,free只是把指针所指的内存释放掉, 并没有删除指针. p1 = NULL;     return head;}void print(struct pass *head){struct pass *temp;temp = head;while(temp != NULL){printf("%d ", temp->number);//如果没有p2->next = NULL, 将导致错误.temp = temp->next;}}int main(){struct pass *head = NULL;head = createList(head);print(head);}

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