第十三章 数据结构基础--单链表

1.1 单链表的创建

尾部加入法创建单链表：头节点、尾节点、中间节点；头节点与尾节点的初始化。

  

#include <stdlib.h>

typedef struct student {
int age;
struct student *next;
}Stu;

Stu *SingleListTailCreate() {
Stu *head = NULL, *tail = NULL, *cur = NULL;
int cycle = 1, x = 0, j = 0;
head = (Stu *)malloc(sizeof(Stu));
head->age = 1;
tail = head;
while(cycle) {
printf("please input data: \n");
scanf("%d", &x);
if (x != 0) {
cur = (Stu *)malloc(sizeof(Stu));
cur->age = x;
tail->next = cur;
tail = cur;
} else {
cycle = 0;
}
}
tail->next = NULL;
return head;

}

1.2 单链表的打印与测长

void PrintSingleList(Stu *head) {
Stu *cur = head;
if (head == NULL)
printf("the list is null.\n");

while (cur != NULL) {
printf("cur->age: %d\n", cur->age);
cur = cur->next;
}
}

int LenSingleList(Stu *head) {
int len = 0;
Stu *cur = head;

if (head == NULL) {
return len;
} 

while (cur != NULL){
cur = cur->next;
len++;
}
return len;
}

1.3 单链表的插入

单链表的插入，必须有专门的指针pre来记录插入时的前驱节点；

以及插入节点cur的前驱与后驱节点的配线。

//index is [1, len-1]
Stu *SingleListInsert(Stu *head, int age, int index) {
int i = 0, len = 0;
Stu *pre = head, *cur = NULL;

if (head == NULL) {
return NULL;
}

len = LenSingleList(head);

if((index < 1) || (index > (len-1))) {
printf("position is wrong.\n");
return head;
}

for (i = 1; i < index; i++) {
pre = pre->next;
}

cur = (Stu *)malloc(sizeof(Stu));
cur->age = age;
//following two lines can not change each other.
cur->next = pre->next;
pre->next = cur;

return head;
}

1.4 单链表的删除

单链表的删除，必须有专门的指针pre来记录删除节点的前驱节点；

以及要删除的节点cur。

Stu *SingleListDel(Stu *head, int age) {
Stu *cur = NULL, *pre= NULL;
if (head == NULL)
return head;

cur = head;

while((cur->age != age) && (cur->next != NULL) ) {
pre = cur;
cur = cur->next;
}

if(cur->age == age) {
if (cur == head) {
head = head->next;
} else {
pre->next = cur->next;
}
free(cur);
} else {
printf("not found.\n");
}
return head;
}

1.5 单链表的逆置

逆置需要指定三节点：前驱节点pre、后驱节点nex与当前节点cur。

Stu *SingleListVerse(Stu *head) {
Stu *pre = NULL, *cur = NULL, *nex = NULL;

if(head == NULL)
return head;

if(head->next == NULL)
return head;

cur = head;
while(cur != NULL) {
nex = cur->next;
cur->next = pre;
pre = cur;
cur = nex;
}
return pre;
}

1.6 单链表的销毁

void FreeSingleList(Stu *head)
{
Stu *temp = NULL;


if (head == NULL) {
return;
}
while (head != NULL) {
temp = head->next;
free(head);
head = temp;
}
}

1.7 单链表的排序

例题1：数组的冒泡排序

冒泡排序的基本思想：两两比较相邻记录的关键字，如果反序则交换，直到没有反序的记录为止。

外循环控制遍历数组的次数；内循环控制相邻两数组的比较次数。

int *Bobble1(int *p, int len) {
int i = 0, j = 0, tmp = 0;

for(i = 0; i < len; i++)
for(j = 0; j < len - i - 1; j++) {
if (p[j] > p[j+1]) {
tmp = p[j];
p[j] = p[j+1];
p[j+1] = tmp;
}
}
return p;
}

例题2： 单链表的冒泡排序

Stu *BobbleList1(Stu *head) {
Stu *cur = NULL;
int i = 0, j = 0, tmp = 0;


if (head == NULL | head->next == NULL)
return head;
int len = LenSingleList(head);
for(i = 0; i < len; i++) {
//locate the head node.
cur = head;
for(j = 0; j < len - i - 1; j++) {
//change the element
if(cur->age > cur->next->age) {
tmp = cur->age;
cur->age = cur->next->age;
cur->next->age = tmp;
}
//node's movement
cur = cur->next;
}
}
return head;
}

1.8 main调用

int main() {
Stu *head = NULL;
int len = 0, age = 2, index = 2;
head = SingleListTailCreate();
PrintSingleList(head);
len = LenSingleList(head);

int a[7] = {1,5,9,6,4,3,4};
Bobble1(a, 7);

head = BobbleList1(head);
printf("After sort: \n");
PrintSingleList(head);
printf("length of list: %d\n", len);

head = SingleListInsert(head, age, index);
PrintSingleList(head);
len = LenSingleList(head);
printf("length of list: %d\n", len);

head = SingleListDel(head, age);
PrintSingleList(head);
len = LenSingleList(head);
printf("length of list: %d\n", len);


head = SingleListVerse(head);
PrintSingleList(head);
len = LenSingleList(head);
printf("length of list: %d\n", len);

FreeSingleList(head);
head = NULL;
len = LenSingleList(head);
printf("length of list: %d\n", len);

return 0;
}

其运行结果如图所示：