先序遍历建立树，算法有了，源代码不知道错在哪里

Question

#include
#include

typedef struct BiTNode
{
char data;//节点数据
struct BiTNode * lchild;//左孩子
struct BiTNode * rchild;//右孩子
}BiTNode, * BiTree;
int CreateBiTree(BiTree T)/*先序构造二叉树*/
{
char ch;
scanf("%c",&ch);
if(ch=='#')
T=NULL;
else
{
T=(BiTree)malloc(sizeof(BiTNode));
if(T==NULL)
{
printf("节点动态分配失败");
return 0;
}
T->data=ch;
CreateBiTree(T->lchild);
CreateBiTree(T->rchild);
}
return 1;
}
int InOrderTraveler( BiTree T )
{
if( NULL!= T )
{
printf( "%c", T -> data );
InOrderTraveler( T -> lchild );
InOrderTraveler( T -> rchild );
}
return 1;
}
int leafcount(BiTree T)/*叶子结点个数*/
{
static int LeafCount= 0;
if(T!=NULL)
{
leafcount(T->lchild);
leafcount(T->rchild);
if(T->lchild==NULL&&T->rchild==NULL)
LeafCount++;
}
return LeafCount;
}
int PostTreeDepth(BiTree T)
{
int hl,hr,max,depth;
if(T!=NULL)
{
hl=PostTreeDepth(T->lchild);/*求左子树深度*/
hr=PostTreeDepth(T->rchild);/*求右子树深度*/
max=hl>hr?hl:hr;/*得到左，右子树深度较大者*/
depth=max+1;
return(depth);/*返回树的深度*/
}
else return 0;/*如果是空树，则返回0*/
}
int BinTreeNodeCount(BiTNode T )/统计结点个数*/
{
int N, num1, num2;

if( T==NULL )
{
    return 0;
}
else
{
    num1 = BinTreeNodeCount( T->lchild );/*统计左子树节点个数*/
    num2 = BinTreeNodeCount( T->rchild );/*统计右子树节点个数*/
    N = num1 + num2 + 1;
    printf("%d",N);
    return N;
}

}

int countDegreeTwo(BiTNode T)/统计度为2的结点个数*/
{
if (T == NULL)
return 0;
if (T->lchild != NULL&& T->rchild != NULL)
return 1 + countDegreeTwo(T->lchild) + countDegreeTwo(T->rchild);
return countDegreeTwo(T->lchild) + countDegreeTwo(T->rchild);
}

int main()
{
BiTree T=NULL;
printf("按先序顺序输入第一个二叉树:");
CreateBiTree(T);
printf("%d",leafcount(T));
printf("%d",BinTreeNodeCount(T));
printf("%d",countDegreeTwo(T));
InOrderTraveler(T);
return 1;
}

Answer 1

你这个错误在于，你想在CreateBiTree函数里改变你main函数的T指针的指向。
要在函数内改变指针的指向必须传二级指针或者一级指针的引用才行。

 #include<stdio.h>
#include<stdlib.h>

typedef struct BiTNode
{
    char data;//节点数据
    struct BiTNode * lchild;//左孩子
    struct BiTNode * rchild;//右孩子
}BiTNode, *BiTree;
int CreateBiTree(BiTree *T)/*先序构造二叉树*/
{
    char ch;
    scanf("%c", &ch);
    if (ch == '#')
        *T = NULL;
    else
    {
        *T = (BiTree)malloc(sizeof(BiTNode));
        if (*T == NULL)
        {
            printf("节点动态分配失败");
            return 0;
        }
        (*T)->data = ch;
        CreateBiTree(&(*T)->lchild);
        CreateBiTree(&(*T)->rchild);
    }
    return 1;
}
int InOrderTraveler(BiTree T)
{
    if (NULL != T)
    {
        printf("%c", T->data);
        InOrderTraveler(T->lchild);
        InOrderTraveler(T->rchild);
    }
    return 1;
}
int leafcount(BiTree T)/*叶子结点个数*/
{
    static int LeafCount = 0;
    if (T != NULL)
    {
        leafcount(T->lchild);
        leafcount(T->rchild);
        if (T->lchild == NULL&&T->rchild == NULL)
            LeafCount++;
    }
    return LeafCount;
}
int PostTreeDepth(BiTree T)
{
    int hl, hr, max, depth;
    if (T != NULL)
    {
        hl = PostTreeDepth(T->lchild);/*求左子树深度*/
        hr = PostTreeDepth(T->rchild);/*求右子树深度*/
        max = hl>hr ? hl : hr;/*得到左，右子树深度较大者*/
        depth = max + 1;
        return(depth);/*返回树的深度*/
    }
    else return 0;/*如果是空树，则返回0*/
}
int   BinTreeNodeCount(BiTNode *T)/*统计结点个数*/
{
    int  N, num1, num2;

    if (T == NULL)
    {
        return 0;
    }
    else
    {
        num1 = BinTreeNodeCount(T->lchild);/*统计左子树节点个数*/
        num2 = BinTreeNodeCount(T->rchild);/*统计右子树节点个数*/
        N = num1 + num2 + 1;
        printf("%d", N);
        return N;
    }
}

int countDegreeTwo(BiTNode *T)/*统计度为2的结点个数*/
{
    if (T == NULL)
        return 0;
    if (T->lchild != NULL&& T->rchild != NULL)
        return 1 + countDegreeTwo(T->lchild) + countDegreeTwo(T->rchild);
    return countDegreeTwo(T->lchild) + countDegreeTwo(T->rchild);
}

int main()
{
    BiTree T = NULL;
    printf("按先序顺序输入第一个二叉树:");
    CreateBiTree(&T);
    printf("%d", leafcount(T));
    printf("%d", BinTreeNodeCount(T));
    printf("%d", countDegreeTwo(T));
    InOrderTraveler(T);
    return 1;
}