排序二叉树删除节点、二叉树后序、先序非递归遍历

#include <bits/stdc++.h>
using namespace std;
typedef char ElemType; 

typedef struct BiNode{
    ElemType data;
    BiNode* lchild;
    BiNode* rchild;     
    BiNode(ElemType data, BiNode* lchild, BiNode* rchild) {
        this->data = data;
        this->lchild = lchild;
        this->rchild = rchild;
    }   
}*BiTree;

stack<BiTree>s;

void postorder(BiTree T){
    BiTree p=T;
    BiTree r=NULL;
    while(p||!s.empty()){
        if(p){
            s.push(p);
            p=p->lchild;
        }
        else{
            p=s.top();
            if(p->rchild&&p->rchild!=r)p=p->rchild;
            else{
                s.pop();
                printf("%c",p->data);
                r=p;
                p=NULL;
            }
        }
    }

}

void preorder(BiTree T){
    while(T||!s.empty()){
        //if(s.empty())printf("q");
        if(T){
            printf("%c",T->data);
            s.push(T);
            T=T->lchild;
        }
        else{
            T=s.top();
            s.pop();
            T=T->rchild;
        }
        

    }
}

void delnode(BiTree &p){
    if(!p->lchild)p=p->rchild;
    else if(!p->rchild)p=p->lchild;
    else{
        BiTree t=p->rchild;
        BiTree q=p;
        while(t->lchild){
            q=t;
            t=t->lchild;
        }
        p->data=t->data;
        if(q==p){
            p->rchild=t->rchild;
            //free(t);
        }
        else{
            q->lchild=t->rchild;
            t=NULL;
        }
    }
}

BiTree findnode(BiTree &T,char x){
    if(!T||T->data==x){
        delnode(T);
        return T;
    }
    if(x<T->data)return findnode(T->lchild,x);
    return findnode(T->rchild,x);
}

int main(){
    /*BiNode* v4 = new BiNode('4', NULL, NULL);
    BiNode* v6 = new BiNode('6', NULL, NULL);
    BiNode* v5 = new BiNode('5', v4, v6);
    BiNode* v1 = new BiNode('1', NULL, NULL);
    BiNode* v3 = new BiNode('3', v1, v5);
    BiNode* v7 = new BiNode('7', v3, NULL);*/
    BiNode* v7 = new BiNode('7', NULL, NULL);
    BiNode* v1 = new BiNode('1', NULL, NULL);
    BiNode* v3 = new BiNode('3', NULL, NULL);
    BiNode* v2 = new BiNode('2', v1, v3);
    BiNode* v5 = new BiNode('5', NULL, NULL);
    BiNode* v6 = new BiNode('6', v5, v7);
    BiNode* v4 = new BiNode('4', v2, v6);
    //BiNode* T = v4;*/
    BiTree T=v7;
    preorder(T);
    printf("
");
    findnode(T,'3');
    preorder(T);
    printf("
");
    postorder(T);
}