一、从指定节点后方插入

插入逻辑如图：

插入前：A指向B，B指向C

插入后：B为插入点，当要插入D时就要让B指向D，D再指向C（插入前B的指向）

#include <stdio.h>struct Test
{int data;struct Test *next;
};void printLink(struct Test *head)
{while(1){if(head != NULL){printf("%d ",head->data);head = head->next;}else{printf("\n");break; }}
}int getLinkNum(struct Test *head)
{int cnt =0;while(head !=NULL){cnt ++;head = head->next;}return cnt;
}int searchLink(struct Test *head,int data)
{while(head != NULL){if(head->data == data){return 1;}head = head->next;}return 0;
}int insertBhind(struct Test *head,int data,struct Test *new)
{struct Test *p = head;        while(p !=NULL){if(p->data == data){new->next = p->next;    //新插入的链表指向插入点的链表p->next = new;          //插入点指向新插入的链表return 1;    }p = p->next;                //循环结束，p指向后面的链表}return 0;
}
int main(){struct Test t1 = {1,NULL};struct Test t2 = {2,NULL};struct Test t3 = {3,NULL};struct Test t4 = {4,NULL};t1.next = &t2;t2.next = &t3;t3.next = &t4;printLink(&t1);int ret =getLinkNum(&t1);printf("total num = %d\n",ret);ret = searchLink(&t1,1);if(ret = 0){printf("没有data = 1\n");}else{printf("有data = 1\n");}struct Test new={100,NULL};      //定义“new”链表insertBhind(&t1,3,&new);        //在数据等于3的位置插入“new”链表printLink(&t1);return 0;
}

二、从指定节点前方插入