程序员面试宝典之数据结构基础----②单链表删除节点(读后）

删除节点比较简单，但要注意两种情况，是否头结点？ ----细节决定成败。

本次删除借助了上篇的创建单链表，代码放在了一块，便于测试。。。。

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
using namespace std;
//notice the define of struct, the node is not a variable,it is the name of the struct.so it can be used to define the struct variable.
//notice the key word of typedef. if there is not the key word ,the node will have different properties.
typedef struct student
{
int data;
struct student* next;
}node;
node* creat()
{
node* head,*p,*s;
int x=0,cycle = 1 ;
head=(node*)malloc(sizeof(node));   //notice the malloc is contained in the lib of <stdlib.h> and must malloc the space for the node before you use it.
p = head;
while(cycle)
{
printf("\nPlease input the data:");
scanf("%d",&x);
if(x!= 0)   // only for test ,so the '0' is the symblo of the end but the value of the node,I ignore this kind of possible. Of course you can do it .
{
s = (node*)malloc(sizeof(node));
s->data = x;
printf("\n%d",s->data);
p->next = s;
p = s;
}
else
cycle = 0;

}
head = head->next;
p->next = NULL;

printf("\n  yyy  %d %d %d %d",head->data,head->next->data,head->next->next->data, head->next->next->next->data);//print four node for test.
return(head);
}
int length(node* head)
{
int n = 0;
node *p;
p = head;
while(p!=NULL)
{
p = p->next;
n++;

}
return n;
}
void print(node* head)
{
node *p;
int n;
n = length(head);
printf("\nNow,These %d records are:",n);
p = head;
if(head!= NULL)
{
while(p != NULL)
{
printf("\n   uuu  %d   ",p->data);
p = p->next;
}
}
}
//删除head单链表中值为num的节点：
node* del_node(node* head ,int num)
{
//注意分两种情况，删除的是头结点或者非头结点
node* p1, *p2;
p2 = head;
while(num != p2->data && NULL != p2->next)
{
p1 = p2;
p2 = p2->next;
}
if(num == p2->data)
{
if(head == p2)
{
head = p2->next;
free(p2);
}
else
{
p1->next = p2->next;
free(p2);
}
}
else
{
printf("%d could not been found ",num);
}
return head;

}
int main()
{
node* head = creat();
print(head);
node* head_new = del_node(head,1);//此处注意，del_node是有返回值的，返回一个新的head，所以，下一个print的时候要给与新的head值。
print(head_new);
}

删除的是头结点的打印结果：

Please input the data:1

1

Please input the data:2

2

Please input the data:3

3

Please input the data:4

4

Please input the data:5

5

Please input the data:6

6

Please input the data:7

7

Please input the data:0

yyy 1 2 3 4

Now,These 7 records are:

uuu 1

uuu 2

uuu 3

uuu 4

uuu 5

uuu 6

uuu 7

Now,These 6 records are:

uuu 2

uuu 3

uuu 4

uuu 5

uuu 6

uuu 7

Process returned 0 (0x0) execution time : 5.081 s

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