二叉树——中序非递归遍历二叉树

利用栈的方法来遍历
先访问将根结点和左子树根结点压栈，然后不断访问左子树，直到NULL，再访问左子树下的右子树，遇到NULL，就出栈。大类的右子树和左子树差不多

思路如下图：

代码

#include <stdio.h>
#include <malloc.h>
typedef struct BiNode{//二叉树结点类型
    char data;
    struct BiNode *lchild,*rchild;
}BiNode,*BiTree;

typedef struct{//栈存储类型
    BiNode **base;//如果不是双指针的话，压栈的时候会显示错误： incompatible types when assigning to type 'BiNode' from type 'BiTree'|，差距就在一个指针
    BiNode **top;
    int stack_size;
}SqStack;

////先序创建
BiTree BiTree_Creat(BiTree T)
{
    char ch;
    scanf("%c",&ch);
    if('#'==ch)
        T=NULL;
    else{
        T=(BiTree)malloc(sizeof(BiNode));
        T->data=ch;
        T->lchild=BiTree_Creat(T->lchild);
        T->rchild=BiTree_Creat(T->rchild);
    }
    return T;
}

SqStack *InitStack(SqStack *S)
{
    if (!(S = (SqStack *)malloc(sizeof(SqStack))))exit(-1);
    S->base=(BiNode **)malloc(100*sizeof(BiNode*));
    if(!S->base)
        printf("error");
    S->top=S->base;
    S->stack_size=100;
    return S;
}

void Push(SqStack *S,BiTree T)
{
    if(S->top-S->base>=S->stack_size)
    {
        S->base=(BiNode **)realloc(S->base,(S->stack_size+10)*sizeof(BiNode*));
        if(!S->base)
            printf("error");
        S->top=S->base+S->stack_size;
        S->stack_size+=10;
    }
    *(S->top)=T;
    S->top++;
}

BiNode** Pop(SqStack *S)
{
   BiNode** e;
   if(S->top==S->base)
        printf("Pop error");
   S->top--;
   e=*S->top;
   return e;
}
int StackEmpty(SqStack *S)
{
    if(S->top==S->base)
        return 1;
    else{
        return 0;
    }
}
void InOrderTraverse(BiTree T,SqStack *S)
{
    BiTree p;
    S=InitStack(S);

    p=T;
    while(p||!StackEmpty(S))
    {
        if(p)
        {
            Push(S,p);
            p=p->lchild;
        }
        else{
            p=Pop(S);
            printf("%c",p->data);
            p=p->rchild;
        }
    }
}

int main()
{
    BiTree T;
    SqStack *S;
    S=InitStack(S);
    T=BiTree_Creat(T);

    printf("中序非递归遍历：\n");
    InOrderTraverse(T,S);
    return 0;
}