单链表在应用中经常用到增加新结点、删除结点、修改结点、查找结点等操作,本文针对上述基本操作做了简单汇总,并给出了详细的算法。
一、在单链表中增加结点
在链表中增加新结点是经常要用到的操作,增加新结点大致可以分为在链表末尾增加、在链表头增加、在中间某个位置增加等三种情形。增加新结点也称为插入新结点。链表结点的接头体如下:
typedef struct Lnode
{
int data; //数据域
struct Lnode *next; //指针域
}LNode;
1.在链表尾插入新结点
假设有单链表如下:
增加元素为3的新结点,得到如下新链表:
算法流程:
1)生成新结点s存储元素3
2)让p指向表头h
3)让p依次后移到链表尾
4)将s链接到p之后
算法:
s = ( LNode* )malloc( sizeof( LNode ) );
s->data = 3;
s->next = NULL;
p = h;
while( p->next != NULL )
{
p = p->next;
p->next = s;
}
2.在链表头插入新结点
在表头插入新结点比较简单,生成新结点之后挂在表头之后即可。
算法为:
s = ( LNode* )malloc( sizeof( LNode ) );
s->data = 3;
s->next = h->next; //此部关键,先把s和结点1链接上。
h->next = s;
3.在链表中间某个位置插入新结点
已有链表如下:
想在元素为4的结点之前插入新结点s,插入过程为:
1)生成新结点s;
2)引入两个临时指针p和q,p通过遍历指向4的结点,q作为p的直接前驱
3)把新结点s插入到q和p之间
算法实现(只考虑了插值成功未考虑失败):
key = 4;
s = ( LNode* )malloc( sizeof( LNode ) );
s->data = 3;
q = h;
p = q->next;
while( p->data != key )
{
q = p;
p = p->next;
}
q->next = s;
s->next = p;
二、在单链表中删除结点
1.删除一个结点
删除元素为3的结点,其算法如下:
key = 3;
q = h;
p = q->next;
while( p != NULL && p->data != key )//当p结点的值不是key,则q和p平行后移,
{
q = p; //q先指向p,之后p再后移
p = p->next;
}
if( p == NULL )
输出链表中无目标结点
else
q->next = p->next;
free( p );
2.删除与某个元素相同的全部结点
删除链表中元素为3的全部结点,则算法为:
key = 3;
q = head;
p = head->next;
//定位
while( p != NULL)
{
if( p->data == key )
{
q->next = p->next;
free(p);
p = q->next;
}
else
{
q = p;
p = p->next;
}
}
3.删除单链表中所有相同的结点
删除单链表中所有值重复的结点,使得所有结点的值都不相同。
算法思路:从单链表的第一个结点开始,对每个结点进行检查:检查链表中该结点的所有后继结点,只要有值和该结点的值相同,则删除之;然后检查下一个结点,直到所有的结点都检查。
算法如下:
ptr = head->next;
while( ptr!= NULL) //检查链表中所有结点
{
q = ptr;
p = ptr->next;
while ( p != NULL ) //检查结点q的所有后继结点p
{
if( p->data == ptr->data )
{
q->next = p->next;
free(p);
p = q->next;
}
else
{
q = p;
p = p->next;
}
}//执行完一轮扫描(可以删除一个相同的值的所有结点),开始下一轮
ptr = ptr->next ;
}
三、修改某个结点
修改链表中第一个值为3的结点中的值为10。算法如下:
newData = 10;
key = 3;
p = h->next;
while( p != NULL && p->data != key )
p = p->next;
if( p == NULL )
输出链表中无目标结点
else
p->data = newData;
free( p );
四、查找某个结点
在单链表中查找值为2的结点
key = 2;
p = h->next;
while( p != NULL && p->data != key )
p = p->next;
if( p == NULL )
输出链表中无目标结点
else
查找成功
五、完整的测试代码
1.代码
#include"stdio.h"
#include"malloc.h"
typedef struct Lnode
{
int data; //数据
struct Lnode *next; //指针域
}LNode;
LNode *CreateLinkListTail( int a[], int n );
void display( LNode *head );
int SearchNode( LNode *head, int key );
void InsertNodeHead( LNode *head, int key );
void InsertNodeTail( LNode *head, int key );
void InsertNode( LNode *head, int key, int e );
void DeleteNode( LNode *head, int key );
void DeleteSameNode( LNode *head, int key );
void DeleteAllSameNode( LNode *head );
void ModifyNode( LNode *head, int key, int newKey );
int main()
{
int a[] = {
1, 6, 4, 3, 5, 6, 1, 6 };
int n = 8;
LNode *head = CreateLinkListTail( a, n );
display( head );
int key = 5;
InsertNodeHead( head, key );
display( head );
InsertNodeTail( head, key );
display( head );
int e = 4;
InsertNode( head, key, e );
display( head );
DeleteNode( head, key );
display( head );
DeleteSameNode( head, key );
display( head );
DeleteAllSameNode( head );
display( head );
int loc = SearchNode( head, key );
if( loc == 0 )
{
printf( " 查找 %d 失败!!!\n", key );
}
else
{
printf( " 查找 %d 成功\n", key );
}
key = 3;
int newKey = 10;
ModifyNode( head, key, newKey );
display( head );
return 0;
}
LNode *CreateLinkListTail( int a[], int n )
{
int i;
LNode *head, *p, *s;
head = (LNode*)malloc(sizeof(LNode));
head->next = NULL;
p = head;
for( i = 0; i < n; i++ )
{
s = (LNode*)malloc(sizeof(LNode));
s->data = a[i];
s->next = NULL;
p->next = s;
p = s;
}
return head;
}
void display( LNode *head )
{
LNode *p;
p = head->next;
printf( " data in linklist: " );
while( p != NULL )
{
printf( "%5d", p->data );
p = p->next;
}
printf( "\n" );
}
int SearchNode( LNode *head, int key )
{
int loc = 0;
LNode *p;
p = head->next;
while( p != NULL )
{
loc++;
if( p->data == key )
{
break;
}
p = p->next;
}
if( p == NULL )
loc = 0;
return loc;
}
void ModifyNode( LNode *head, int key, int newKey )
{
LNode *p;
p = head->next;
while( p != NULL && p->data != key )
{
p = p->next;
}
if( p == NULL )
printf( "%d 不在链表中\n", key );
else
{
p->data = newKey;
}
}
void InsertNodeHead( LNode *head, int key )
{
LNode *s = (LNode*)malloc(sizeof(LNode));
s->data = key;
s->next = head->next;
head->next = s;
}
void InsertNodeTail( LNode *head, int key )
{
LNode *p, *s;
s = (LNode*)malloc(sizeof(LNode));
s->data = key;
s->next = NULL;
p = head;
while( p->next != NULL )
{
p = p->next;
}
p->next = s;
}
void InsertNode( LNode *head, int key, int e )
{
LNode *p, *q, *s;
//先定位key所在的节点
//插入新节点
q = head; //q是p的直接前驱节点
p = head->next;
while( p != NULL )
{
if( p->data == e )
{
s= ( LNode * )malloc( sizeof( LNode ) );
s->data = key;
s->next = p->next;
p->next = s;
break;
}
q = p;
p = p->next;
}
if( p == NULL )
{
s= ( LNode * )malloc( sizeof( LNode ) );
s->data = e;
s->next = NULL;
q->next = s;
}
}
void DeleteNode( LNode *head, int key )
{
LNode *p, *q;
q = head;
p = head->next;
//定位
while( p != NULL )
{
if( p->data == key )
{
q->next = p->next;
free(p);
break;
}
q = p;
p = p->next;
}
}
void DeleteSameNode( LNode *head, int key )
{
LNode *p, *q;
q = head;
p = head->next;
//定位
while( p != NULL)
{
if( p->data == key )
{
q->next = p->next;
free(p);
p = q->next;
}
else
{
q = p;
p = p->next;
}
}
}
void DeleteAllSameNode( LNode *head )
{
LNode *ptr = head->next, *q, *p;
while( ptr!= NULL) //检查链表中所有结点
{
q = ptr;
p = ptr->next;
while ( p != NULL ) //检查结点q的所有后继结点p
{
if( p->data == ptr->data )
{
q->next = p->next;
free(p);
p = q->next;
}
else
{
q = p;
p = p->next;
}
}//执行完一轮扫描(可以删除一个相同的值的所有结点),开始下一轮
ptr = ptr->next ;
}
}
2.测试结果