二叉树的创建及遍历_递归遍历_非递归遍历

#include <iostream>
#include <cstdio>
#include <malloc.h>
#include <stack>

using namespace std;

typedef struct tree{
    char a;
    tree *lchild;
    tree *rchild;
};

tree* create(tree *T){

    char c=getchar();
    if(c=='#'){
        T=NULL;
    }else{

        T=(tree*)malloc(sizeof(tree));
        T->a=c;
        if(!T){
            printf("\Error!n");
        }
        T->lchild=create(T->lchild);
        T->rchild=create(T->rchild);
    }
    return T;

}

void preorder(tree *T){
    if(T){
        printf("%c",T->a);
        preorder(T->lchild);
        preorder(T->rchild);
    }
}

void inorder(tree *T){
    if(T){
        inorder(T->lchild);
        printf("%c",T->a);
        inorder(T->rchild);
    }
}

void postorder(tree *T){
    if(T){
        postorder(T->lchild);
        postorder(T->rchild);
        printf("%c",T->a);
    }
}

//非递归先序遍历
void preorder1(tree *T){
    tree *p=T;
    stack<tree *> s;
    while(p!=NULL||!s.empty()){
        while(p!=NULL){
            printf("%c",p->a);
            s.push(p);
            p=p->lchild;
        }
        if(!s.empty()){
            p=s.top();
            s.pop();
            p=p->rchild;
        }
    }
}


//非递归中序遍历
void inorder1(tree *T){
    tree *p=T;
    stack<tree *> s;
    while(p!=NULL||!s.empty()){
        while(p!=NULL){
            s.push(p);
            p=p->lchild;
        }
        if(!s.empty()){
            p=s.top();
            printf("%c",p->a);
            s.pop();
            p=p->rchild;
        }
    }
}

//非递归后序遍历



int main()
{
    tree *T;
    printf("Plese input the tree's sequence:\n");
    T=create(T);
    printf("preorder:    ");
    preorder(T);
    printf("\n");

    printf("inorder:     ");
    inorder(T);
    printf("\n");

    printf("postorder:   ");
    postorder(T);
    printf("\n");


    printf("preorder(no_recersive):    ");
    preorder1(T);
    printf("\n\n");

    printf("inorder(no_recersive):     ");
    inorder1(T);
    printf("\n\n");

    return 0;
}