线性表之单链表
将线性表L=(a0,a1,……,an-1)中各元素分布在存储器的不同存储块,称为结点,通过地址或指针建立元素之间的联系结点的data域存放数据元素ai,而next域是一个指针,指向ai的直接后继ai+1所在的结点设p指向链表中结点ai
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文章目录
线性表的链式存储结构
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将线性表L=(a0,a1,……,an-1)中各元素分布在存储器的不同存储块,称为结点,通过地址或指针建立元素之间的联系

-
结点的data域存放数据元素ai,而next域是一个指针,指向ai的直接后继ai+1所在的结点

- 节点类型描述:
typedef struct node {
data_t data; //结点的数据域//
struct node *next; //结点的后继指针域//
} listnode, *linklist;
- 设p指向链表中结点ai

- 获取ai,写作:p->data
- 而取ai+1,写作:p->next->data
- 若指针p的值为NULL,则它不指向任何结点,此时取p->data或p->next是错误的
- 调用C语言中malloc()函数向系统申请结点的存储空间
linklist p;p = (linklist)malloc(sizeof(listnode))
- 则创建一个类型为linklist的结点,且该结点的地址已存入指针变量p中:

单链表创建
- 依次读入表L=(a0,…,an-1)中每一元素ai(假设为整型),若ai≠结束符(-1),则为ai创建一结点,然后插入表尾,最后返回链表的头结点指针H
- 设L=(2,4,8,-1),则建表过程如下:

- 链表的结构是动态形成的,即算法运行前,表结构是不存在的
单链表查找
按序号查找
- 实现GetLinklist(h, i)运算
- 算法思路:从链表的a0起,判断是否为第i结点,若是则返回该结点的指针,否则查找下一结点,依次类推
按值查找(定位)
- 即实现Locate(h, x)
- 算法思路:从链表结点a0起,依次判断某结点是否等于x,若是,则返回该结点的地址,若不是,则查找下一结点a1,依次类推。若表中不存在x,则返回NULL
单链表插入
- 即实现InsertLinklist(h, x, i,),将x插入表中结点ai之前的情况
- 算法思路:调用算法GetLinklist(h, i-1),获取结点ai-1的指针p(ai 之前驱),然后申请一个q结点,存入x,并将其插入p指向的结点之后

单链表删除
- 即实现DeleteLinklist(h, i)
- 算法思路:同插入法,先调用函数GetLinklist(h, i-1),找到结点ai的前驱,然后将结点ai删除

单链表倒置
- 算法思路:依次取原链表中各结点,将其作为新链表首结点插入H结点之后

求相邻两结点data值之和为最大的第一结点指针
- 设结点data域为整型,求链表中相邻两结点data值之和为最大的第一结点的指针
- 算法思路:设p,q 分别为链表中相邻两结点指针,求p->data+q->data为最大的那一组值,返回其相应的指针p即可

合并链表且有序递增
- 设两单链表A、B按data值(设为整型)递增有序,将表A和B合并成一表A,且表A也按data值递增有序
- 算法思路:设指针p、q分别指向表A和B中的结点,若p->data ≤q->data则p结点进入结果表,否则q结点进入结果表

代码实现
功能代码
#include <stdio.h>
#include <stdlib.h>
#include "linklist.h"
linklist list_create() {
linklist H;
H = (linklist)malloc(sizeof(listnode));
if (H == NULL) {
printf("malloc failed\n");
return H;
}
H->data = 0;
H->next = NULL;
return H;
}
int list_tail_insert(linklist H, data_t value) {
linklist p;
linklist q;
if (H == NULL) {
printf("H is NULL\n");
return -1;
}
if ((p = (linklist)malloc(sizeof(listnode))) == NULL) {
printf("malloc failed\n");
return -1;
}
p->data = value;
p->next = NULL;
q = H;
while (q->next != NULL) {
q = q->next;
}
q->next = p;
return 0;
}
linklist list_get(linklist H, int pos) {
linklist p;
int i;
if (H == NULL) {
printf("H is NULL\n");
return NULL;
}
if (pos == -1) {
return H;
}
if (pos < -1) {
printf("pos is invalid\n");
return NULL;
}
p = H;
i = -1;
while (i < pos) {
p = p->next;
if (p == NULL) {
printf("pos is invalid\n");
return NULL;
}
i++;
}
return p;
}
int list_insert(linklist H, data_t value, int pos) {
linklist p;
linklist q;
if (H == NULL) {
printf("H is NULL\n");
return -1;
}
p = list_get(H, pos-1);
if (p == NULL) {
return -1;
}
if ((q = (linklist)malloc(sizeof(listnode))) == NULL) {
printf("malloc failed\n");
return -1;
}
q->data = value;
q->next = NULL;
q->next = p->next;
p->next = q;
return 0;
}
int list_delete(linklist H, int pos) {
linklist p;
linklist q;
if (H == NULL) {
printf("H is NULL\n");
return -1;
}
p = list_get(H, pos-1);
if (p == NULL)
return -1;
if (p->next == NULL) {
printf("delete pos is invalid\n");
return -1;
}
q = p->next;
p->next = q->next;//p->next = p->next->next;
printf("free:%d\n", q->data);
free(q);
q = NULL;
return 0;
}
int list_show(linklist H) {
linklist p;
if (H == NULL) {
printf("H is NULL\n");
return -1;
}
p = H;
while (p->next != NULL) {
printf("%d ", p->next->data);
p = p->next;
}
puts("");
return 0;
}
linklist list_free(linklist H) {
linklist p;
if (H == NULL)
return NULL;
p = H;
printf("free:");
while (H != NULL) {
p = H;
printf("%d ", p->data);
free(p);
H = H->next;
}
puts("");
return NULL;
}
int list_reverse(linklist H) {
linklist p;
linklist q;
if (H == NULL) {
printf("H is NULL\n");
return -1;
}
if (H->next == NULL || H->next->next == NULL) {
return 0;
}
p = H->next->next;
H->next->next = NULL;
while (p != NULL) {
q = p;
p = p->next;
q->next = H->next;
H->next = q;
}
return 0;
}
linklist list_adjmax(linklist H, data_t *value) {
linklist p, q, r;
data_t sum;
if (H == NULL){
printf("H is NULL\n");
return NULL;
}
if (H->next == NULL || H->next->next == NULL || H->next->next->next == NULL) {
return H;
}
q = H->next;
p = H->next->next;//p = q->next;
r = q;
sum = q->data + p->data;
while (p->next != NULL) {
p = p->next;
q = q->next;
if (sum < q->data + p->data) {
sum = q->data + p->data;
r = q;
}
}
*value = sum;
return r;
}
int list_merge(linklist H1, linklist H2) {
linklist p, q, r;
if (H1 == NULL || H2 == NULL) {
printf("H1 || H2 is NULL\n");
return -1;
}
p = H1->next;
q = H2->next;
r = H1;
H1->next = NULL;
H2->next = NULL;
while (p && q) {
if (p->data <= q->data) {
r->next = p;
p = p->next;
r = r->next;
r->next = NULL;
} else {
r ->next = q;
q = q->next;
r = r->next;
r->next = NULL;
}
}
if (p == NULL) {
r->next = q;
}else {
r->next = p;
}
return 0;
}
头文件
typedef int data_t;
typedef struct node {
data_t data;
struct node * next;
}listnode, * linklist;
linklist list_create();
int list_tail_insert(linklist H, data_t value);//head
linklist list_get(linklist H, int pos);
int list_insert(linklist H, data_t value, int pos);
int list_delete(linklist H, int pos);
int list_show(linklist H);
linklist list_free(linklist H);
int list_reverse(linklist H);
linklist list_adjmax(linklist H, data_t *value);
int list_merge(linklist H1, linklist H2);
测试用例
#include <stdio.h>
#include "linklist.h"
void test_get();
void test_insert();
void test_delete();
void test_reverse();
void test_adjmax();
int main(int argc, const char *argv[])
{
linklist H1, H2;
int a[] = {1, 4, 6, 8, 10};
int b[] = {2, 4, 16, 18, 30};
int i;
H1 = list_create();
if (H1 == NULL)
return;
H2 = list_create();
if (H2 == NULL)
return;
for (i = 0; i < sizeof(a)/sizeof(int); i++) {
list_tail_insert(H1, a[i]);
}
for (i = 0; i < sizeof(b)/sizeof(int); i++) {
list_tail_insert(H2, b[i]);
}
list_show(H1);
list_show(H2);
list_merge(H1, H2);
printf("merge:\n");
list_show(H1);
list_show(H2);
list_free(H1);
list_free(H2);
return 0;
}
void test_adjmax() {
linklist H;
linklist r;
int value;
int sum;
H = list_create();
if (H == NULL)
return;
printf("input:");
while (1) {
scanf("%d", &value);
if (value == -1)
break;
list_tail_insert(H, value);
printf("input:");
}
list_show(H);
r = list_adjmax(H, &sum);
if (r != NULL && r != H) {
printf("data=%d, sum=%d\n", r->data, sum);
}
list_show(H);
list_free(H);
}
void test_reverse() {
linklist H;
int value;
H = list_create();
if (H == NULL)
return ;
printf("input:");
while (1) {
scanf("%d", &value);
if (value == -1)
break;
list_tail_insert(H, value);
printf("input:");
}
list_show(H);
list_reverse(H);
list_show(H);
list_free(H);
}
void test_delete() {
linklist H;
int value;
H = list_create();
if (H == NULL)
return;
printf("input:");
while (1) {
scanf("%d", &value);
if (value == -1)
break;
list_tail_insert(H, value);
printf("input:");
}
list_show(H);
printf("H=%p\n", H);
H = list_free(H);
printf("H=%p\n", H);
list_delete(H, -4);//1 3 5 7
list_show(H);
list_free(H);
}
void test_get() {
linklist H;
int value;
linklist p;
H = list_create();
if (H == NULL)
return;
printf("input:");
while (1) {
scanf("%d", &value);
if (value == -1)
break;
list_tail_insert(H, value);
printf("input:");
}
list_show(H);
p = list_get(H, 4);//1 3 5 7
if (p != NULL)
printf("value=%d\n", p->data);
}
void test_insert() {
linklist H;
int value;
H = list_create();
if (H == NULL)
return;
printf("input:");
while (1) {
scanf("%d", &value);
if (value == -1)
break;
list_tail_insert(H, value);
printf("input:");
}
list_show(H);
list_insert(H, 100, 0);//1 3 5 7
list_show(H);
}
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