如何按中序、后序建立一棵二叉树？

用空格表示空节点。
如果不空格的话，怎么做？

http://blog.csdn.net/zhaojinjia/article/details/9314989

#include"stdio.h"
#include"malloc.h"
#include"stdlib.h"
typedef struct lNode
{
char data;
struct lNode *lchild;
struct lNode *rchild;
}LNODE,*Tree;

typedef struct Node
{
Tree data;
struct Node * Next;
}NODE, * PNODE;

typedef struct Stack
{
PNODE pBottom;
PNODE pTop;
}STACK, * PSTACK;

//函数声明
PSTACK initStack(void);//创建栈
void push(PSTACK S,Tree val);//压栈
void pop(PSTACK S);//出栈
bool stackEmpty(PSTACK pS);

Tree CreateBiTree();//建树
void pretraverse(Tree T);//先序递归遍历
void Intraverse(Tree T);//中序递归遍历
void posttraverse(Tree T);//后序递归遍历
void NoIntraverse(Tree T);//中序非递归遍历

int main()
{
Tree T;
T=CreateBiTree();

pretraverse(T);printf("\n");

Intraverse(T);
printf("\n");

posttraverse(T);printf("\n");

NoIntraverse(T);printf("\n");

return 0;
}
//建树
Tree CreateBiTree()
{
char ch;
Tree T;
scanf("%c",&ch);
if(ch=='#')T=NULL;
else{
T = (Tree)malloc(sizeof(LNODE));
T->data = ch;
T->lchild = CreateBiTree();
T->rchild = CreateBiTree();
}
return T;//返回根节点
}

//先序递归遍历(遍历顺序：根左右)
void pretraverse(Tree T)
{
if(T!=NULL)
{
printf("%c",T->data);//输出根节点数据
pretraverse(T->lchild);//遍历左子树
pretraverse(T->rchild);//遍历右子树
}
}
//中序递归遍历(遍历顺序：左根右)
void Intraverse(Tree T)
{
if(T!=NULL)
{
Intraverse(T->lchild);//遍历左子树
printf("%c",T->data);//输出根节点数据
Intraverse(T->rchild);//遍历右子树

}
}
//后序递归遍历(遍历顺序：左右根)
void posttraverse(Tree T)
{
if(T!=NULL)
{
posttraverse(T->lchild);//遍历左子树
posttraverse(T->rchild);//遍历右子树
printf("%c",T->data);//输出根节点数据

}
}

//中序遍历（非递归遍历）
void NoIntraverse(Tree T)
{
PSTACK s;
s=initStack();
Tree p=T;
while(p!=NULL||!stackEmpty(s))
{
while(p)
{
push(s,p);
p=p->lchild;
}
if(!stackEmpty(s))
{
pop(s);

p=p->rchild;
}
}
}
PSTACK initStack(void)
{
PSTACK pS;
pS->pTop=(PNODE)malloc(sizeof(NODE));
if(pS->pTop==NULL)
{
printf("动态内存分配失败！");
exit(-1);
}
else
{
pS->pBottom=pS->pTop;
pS->pBottom->Next=NULL;

}
return pS;
}
void push(PSTACK pS,Tree val)
{
PNODE q;
q=(PNODE)malloc(sizeof(NODE));
if(q==NULL)
{
printf("动态内存分配失败！");
exit(-1);
}
else
{
q->data=val;
q->Next=pS->pTop;
pS->pTop=q;
}

}
void pop(PSTACK pS)
{
PNODE q;
if(pS->pTop==NULL)
{
printf("动态内存分配失败！");
exit(-1);
}
else
{
q=pS->pTop;
printf("%c",q->data);
pS->pTop=q->Next;
free(q);

}

}
bool stackEmpty(PSTACK pS)
{
if(pS->pTop==pS->pBottom)
{
return true;
}
return false;
}

希望对你有帮助，如有疑问一起学习