单链表的定义及空指针头插法

单链表定义

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typedef struct node_s {
	int val;
	struct node_s* next;
}Node;

头插法

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void add_to_head(Node** list, int val) {		//因为要改变头指针指向，需要一个指向头指针地址的指针，即二级指针
	Node** head = list;
	Node* newNode = (Node*)malloc(sizeof(Node));
	newNode->val = val;
	newNode->next = NULL;
	
	newNode->next = *head;
	*head = newNode;
}

设置带有头指针的单链表

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

typedef struct node_s {
	int val;
	struct node_s* next;
}Node;

void add_to_head(Node** head,int val);

int main() {
	Node* list = NULL;

	add_to_head(&list, 1);
	add_to_head(&list, 2);
	add_to_head(&list, 3);
	add_to_head(&list, 4);
	add_to_head(&list, 5);

	for (Node* head = list; head != NULL; head = head->next) {
		printf("%d ", head->val);
	}

	return 0;
}

void add_to_head(Node** list, int val) {	
	Node** head = list;
	Node* newNode = (Node*)malloc(sizeof(Node));
	newNode->val = val;
	newNode->next = NULL;
	
	newNode->next = *head;
	*head = newNode;
}

运行结果