原题链接：数据结构-链表的基本操作
前插法初始化链表
#include<stdio.h>#include<stdlib.h>#include<string.h>int len = 0;typedef struct Node {int data;struct Node *next;}LinkList;LinkList *IntiList(int n)//若倒置需要前插法初始化{LinkList *phead;//开辟一个头指针(无需开辟头结点)phead = NULL;//注意初始化头指针for (int i = 0; i < n; i++){LinkList *p = (LinkList*)malloc(sizeof(LinkList));//开辟一个新结点scanf("%d", &p->data);p->next = NULL;if (phead == NULL){//如果链表为空,则把新开的第一个结点做头结点phead = p;}else{//前插法p->next = phead;phead = p；}len++;}return phead;}
插入操作的注意事项
1.若链表为空,则当插入位置为1时,插入成功。
2.若插入位置大于长度，则插入失败
3.插入需找到要插入的位置之前的位置
LinkList *insert(LinkList *phead)//一定要返回phead{LinkList *p = phead;int n, m;scanf("%d %d", &n, &m);if(n>len){if (len == 0)//特殊判断长度为0的情况{if (n == 1){LinkList *pNode = (LinkList *)malloc(sizeof(LinkList));pNode->data = m;phead = pNode;pNode->next = NULL;len++;printf("insert OK\n");return phead;}else {printf("insert fail\n");return phead;}}}else{if (n == 1)//如果链表不为空，又想在头部插入{LinkList *pNode = (LinkList *)malloc(sizeof(LinkList));pNode->next = phead;pNode->data = m;phead = pNode;}else if(n==len)//想在尾部之前插入一个数{for (int i = 1; i < len-1; i++)p = p->next;LinkList *pNode = (LinkList *)malloc(sizeof(LinkList));pNode->data = m;pNode->next = p->next;p->next = pNode;}else {for (int i = 1; i < n-1; i++)//在中间任意位置插入，先找到插入位置之前p->next = p;LinkList *pNode = (LinkList *)malloc(sizeof(LinkList));pNode->data = m;pNode->next = p->next;p->next = pNode;}len++;printf("insert OK\n");return phead;}}
//获取元素
int get(LinkList *phead){int n = 0;scanf("%d", &n);LinkList*p = phead;if (n > len){printf("get fail");return 0;}else {for (int i = 1; i < n; i++){p = p->next;}printf("%d\n", p->data);}}
删除操作:与插入操作一样，找到需删除节点位置的前一个
头结点与尾结点需要特殊处理
LinkList* Delete(LinkList *phead){LinkList *p = phead;int n = 0;scanf("%d", &n);if (n > len){printf("delete fail\n");return 0;}else {if (n == 1)//n==1时特殊判断{phead = p->next;free(p);}else if (n == len)//想删除最后一个节点{for (int i = 1; i < len-1; i++)//循环一定是从1到n-1。{p = p->next;}p->next = NULL;}else{for (int i = 1; i < n-1; i++)//欲删除n，则从i=1开始移动n-1次到n之前//先找到待删除的前一个位置p = p->next;//现在p在待删除节点之前LinkList *q = p->next;p->next = p->next->next;free(q);}}len--;printf("delete OK\n");return phead;}
显示链表
void show(LinkList *phead){if (len == 0){printf("Link list is empty\n");}else{LinkList *p = phead;while (p!= NULL){printf("%d ", p->data);p = p->next;}printf("\n");}}
以下是完整代码
#include<stdio.h>#include<stdlib.h>#include<string.h>int len = 0;typedef struct Node {int data;struct Node *next;}LinkList;LinkList *IntiList(int n)//前插法初始化{LinkList *phead;//开辟节点和开辟指针是两个意思！！！！phead = NULL;for (int i = 0; i < n; i++){LinkList *p = (LinkList*)malloc(sizeof(LinkList));scanf("%d", &p->data);p->next = NULL;if (phead == NULL){phead = p;}else{p->next = phead;phead = p;}len++;}return phead;}LinkList *insert(LinkList *phead)//一定要返回phead{LinkList *p = phead;int n, m;scanf("%d %d", &n, &m);if(n>len){if (len == 0){if (n == 1){LinkList *pNode = (LinkList *)malloc(sizeof(LinkList));pNode->data = m;phead = pNode;pNode->next = NULL;//插入len++;printf("insert OK\n");return phead;}else {printf("insert fail\n");return phead;}}}else{if (n == 1){LinkList *pNode = (LinkList *)malloc(sizeof(LinkList));pNode->next = phead;pNode->data = m;phead = pNode;}else if(n==len)//想在尾部之前插入一个数{for (int i = 1; i < len-1; i++){p = p->next;}LinkList *pNode = (LinkList *)malloc(sizeof(LinkList));pNode->data = m;pNode->next = p->next;p->next = pNode;//找到尾部之前}else {//在中间插入for (int i = 1; i < n-1; i++)//在n插入{p->next = p;}LinkList *pNode = (LinkList *)malloc(sizeof(LinkList));pNode->data = m;pNode->next = p->next;p->next = pNode;}len++;printf("insert OK\n");return phead;}//插入尾巴//插入头部//插入中间}int get(LinkList *phead){int n = 0;scanf("%d", &n);LinkList*p = phead;if (n > len){printf("get fail");return 0;}else {for (int i = 1; i < n; i++){p = p->next;}printf("%d\n", p->data);}}LinkList* Delete(LinkList *phead)//这里传入的是指针形参,该指针移动不会影响原来的头指针，但如果释放该指针指向的空间，则原来指针的指向也为空{LinkList *p = phead;int n = 0;scanf("%d", &n);if (n > len){printf("delete fail\n");return 0;}else {if (n == 1){phead = p->next;free(p);}else if (n == len)//想删除最后一个节点{for (int i = 1; i < len-1; i++)//i=1,一定是n-1！{p = p->next;}p->next = NULL;}else{for (int i = 1; i < n-1; i++)//欲删除n，则从1开始移动n-1次到n之前//先找到待删除的前一个位置p = p->next;//现在p在待删除节点之前LinkList *q = p->next;p->next = p->next->next;free(q);}//头删，尾删，中间删除}len--;printf("delete OK\n");return phead;}void show(LinkList *phead){if (len == 0){printf("Link list is empty\n");}else{LinkList *p = phead;while (p!= NULL){printf("%d ", p->data);p = p->next;}printf("\n");}}int main(){int n = 0,m=0;scanf("%d", &n);LinkList *phead = IntiList(n);scanf("%d", &m);while (m--){char str[200];scanf("%s", str);if (strcmp(str, "show") == 0){show(phead);}else if (strcmp(str, "get") == 0){get(phead);}else if (strcmp(str, "delete") == 0){phead=Delete(phead);}else if (strcmp(str, "insert") == 0){phead = insert(phead);}}}
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