C语言：链表插入
链表的插入分为头插入，中间插入和尾插入。
具体方法如下：
#include<stdio.h>
#include<stdlib.h>typedef struct node
{int s;struct node* pnext;
}list;list* addnode(list** pphead, list** ppend, int n)
{list* ptemp = malloc(sizeof(list));ptemp->s = n;ptemp->pnext = NULL;if (NULL == *pphead){*pphead = ptemp;*ppend = ptemp;}else{(*ppend)->pnext = ptemp;*ppend = ptemp;}
}void insertnode(list** pphead, list** ppend, list* pnode, int val)
{//头插入//新来节点的下一个指向头节点//头指针指向新来的节点（新来的节点成为新的头节点）if ((*pphead)->s == val){pnode->pnext = *pphead;*pphead = pnode;return;}//中间插入//遍历链表//找到插入位置的前一个结点//新来结点的下一个指向标记的下一个//标记的下一个指向新来的节点list* pmark = *pphead;while (pmark->pnext!= NULL){if (pmark->pnext->s == val){pnode->pnext = pmark->pnext;pmark->pnext = pnode;return;}pmark = pmark->pnext;}//尾插入//尾节点的下一个指向新来的节点//尾指针指向新来的节点（新来的节点成为新的尾节点）(*ppend)->pnext = pnode;*ppend = pnode;
}int main()
{list* phead = NULL;//定义头指针list* pend = NULL; //定义尾指针//先添加几个节点addnode(&phead, &pend, 1);addnode(&phead, &pend, 2);addnode(&phead, &pend, 3);addnode(&phead, &pend, 4);//创建一个节点list* ptep = malloc(sizeof(list));ptep->s = 7;ptep->pnext = NULL;//将创建的节点插入insertnode(&phead, &pend, ptep, 5);//遍历链表，检验是否成功插入while (phead != NULL){printf("%d\n", phead->s);phead = phead->pnext;}return 0;
}