初学数据结构，在链表的合成中想尝试不用结点，发现不管咋样都是错误的。
下面是代码
typedef int ElementType;
typedef struct Node *PtrToNode;
struct Node {
ElementType Data;
PtrToNode Next;
};
typedef PtrToNode List;
List Read();
void Print( List L );
List Merge( List L1, List L2 ); //对两个有序链表进行合并
//链表均带有头结点
int main()
{
List L1, L2, L;
L1 = Read();
L2 = Read();
L = Merge(L1, L2);
Print(L);
Print(L1);
Print(L2);
return 0;
}
List Read()
{
int n;
scanf("%d",&n);
List L=(List)malloc(sizeof(PtrToNode)); ///申请一个头结点
L->Next = NULL; ///头指针为空
if(n) ///当n不是0时
{
List r=L; ///r是一个中间变量的节点
for(int i=0;i<n;i++)
{
List p=(List)malloc(sizeof(struct Node));
scanf("%d",&(p->Data)); ///尾插法
r->Next = p;
r = p;
}
r->Next = NULL;
}
return L;
}
void Print( List L )
{
List p=L->Next;
if(p)
{
List r;
r = L;
while(r->Next)
{
r = r->Next;
printf("%d ",r->Data);
}
}
else
{
printf("NULL");
}
printf("\n ");
}
List Merge( List L1, List L2 )
{
List L,p,a,b;
L = (List)malloc(sizeof(struct Node));
p = L->Next;
a = L1->Next;
b = L2->Next;
while(a && b)
{
if(a->Data < b->Data)
{
p->Data = a->Data;
p = p->Next;
a = a->Next;
}
else if(a->Data == b->Data)
{
p->Data = a->Data;
p = p->Next;
a = a->Next;
b = b->Next;
}
else
{
p->Data = b->Data;
p = p->Next;
b = b->Next;
}
}
for( ;a;a = a->Next)
{
p->Data = a->Data;
p = p->Next;
}
for( ;b;b = b->Next)
{
p->Data = L2->Data;
p = p->Next;
}
L1->Next = NULL;
L2->Next = NULL;
p = NULL;
return L;
}
l = (List)malloc(sizeof(struct Node));
p = l->Next;
这里就错了
l没有初始化，next是野指针
你把完整程序包括main都贴出来，输入输出贴出来，代码格式化好（点</>然后放入代码），再帮你调试。
大概知道了问题所在，后面自己改了下代码。但其中一个还是有错误。也发现这个不用结点的方式真的是太浪费空间，太傻了。发现还有两个地方不太懂？
一 L = (List)malloc(sizeof(struct Node));L->Next = NULL;中为什么L的next初始化为空后，L就是初始化了？
二 如果仅对L用malloc分配内存不能算初始化指针吗？
自己理解：查了malloc函数（malloc 向系统申请分配指定size个字节的内存空间。返回类型是 void* 类型。void* 表示未确定类型的指针。C,C++规定，_void* 类型可以强制转换为任何其它类型的指针）那L = (List)malloc(sizeof(struct Node));是否只是对L初始化，而Next并没有初始化导致的错误。另外代码中中的p,a,b，temp在利用完后是否应该再利用free进行释放，以便减少空间内存的占用。
_**
List Merge( List L1, List L2 )
{
List L,p,a,b;
List temp;
L = (List)malloc(sizeof(struct Node));
L->Next = NULL;
p = L;
a = L1->Next;
b = L2->Next;
while(a && b)
{
if(a->Data < b->Data)
{
temp = (List)malloc(sizeof(struct Node));
temp->Next = NULL;
temp->Data = a->Data;
p->Next = temp;
p = p->Next;
a = a->Next;
}
else if(a->Data == b->Data)
{
temp = (List)malloc(sizeof(struct Node));
temp->Next = NULL;
temp->Data = a->Data;
p->Next = temp;
p = p->Next;
a = a->Next;
b = b->Next;
}
else
{
temp = (List)malloc(sizeof(struct Node));
temp->Next = NULL;
temp->Data = b->Data;
p->Next = temp;
p = p->Next;
b = b->Next;
}
}
for( ;a;a = a->Next)
{
temp = (List)malloc(sizeof(struct Node));
temp->Next = NULL;
temp->Data = a->Data;
p->Next = temp;
p = p->Next;
}
for( ;b;b = b->Next)
{
temp = (List)malloc(sizeof(struct Node));
temp->Next = NULL;
temp->Data = b->Data;
p->Next = temp;
p = p->Next;
}
L1->Next = NULL;
L2->Next = NULL;
return L;
}
/*List Merge( List L1, List L2 ) 不借用中间变量temp的改写 运行错误
{
List L,p,a,b;
L = (List)malloc(sizeof(struct Node));
L->Next = (List)malloc(sizeof(struct Node));
L->Next->Next = NULL;
p = L->Next;
a = L1->Next;
b = L2->Next;
while(a && b)
{
if(a->Data < b->Data)
{
p->Data = a->Data;
p->Next = (List)malloc(sizeof(struct Node));
p->Next->Next = NULL;
p = p->Next;
a = a->Next;
}
else if(a->Data == b->Data)
{
p->Data = a->Data;
p->Next = (List)malloc(sizeof(struct Node));
p->Next->Next = NULL;
p = p->Next;
a = a->Next;
b = b->Next;
}
else
{
p->Data = b->Data;
p->Next = (List)malloc(sizeof(struct Node));
p->Next->Next = NULL;
p = p->Next;
b = b->Next;
}
}
for( ;a;a = a->Next)
{
p->Data = a->Data;
p->Next = (List)malloc(sizeof(struct Node));
p->Next->Next = NULL;
p = p->Next;
}
for( ;b;b = b->Next)
{
p->Data = L2->Data;
p->Next = (List)malloc(sizeof(struct Node));
p->Next->Next = NULL;
p = p->Next;
}
L1->Next = NULL;
L2->Next = NULL;
p = NULL;
return L;
}*/