二叉树的先序建立与非递归遍历C++版_非递归先序遍历二叉树c++-优快云博客

本文详细介绍了如何通过非递归方式实现二叉树的先序、中序和后序遍历，包括使用栈的数据结构进行操作，避免了递归带来的内存消耗，展示了算法在数据结构领域的巧妙应用。

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#include<iostream>
using namespace std;
class tree
{
    public:
    char data;
    int tag;
    class tree *lchild;
    class tree *rchild;
};
tree* build()//先序建树
{
    char c;
    cin>>c;
    tree *t;
    if(c=='#')
    {
           t=NULL;
    }
    else
    {
        t=new tree;
        t->data=c;
        t->lchild = build();
        t->rchild = build();
    }
    return t;
}
class stack
{
    public:
    tree *top,*base;
};
void init (stack *s)//初始化栈
{
    s->base=new tree[100];
    s->top=s->base;
}
void push(stack *s,tree *t)//入栈
{
     *(s->top++)=*t;
}
void pop(stack *s,tree *&t)//删除栈顶元素
{
     *t=*(--(s->top));
}
void gettop(stack *s,tree *&t)//取栈顶元素
{
    *t= *(s->top-1);
}
void preorder(tree *t)//非递归先序遍历
{
    stack *s=new stack;
    tree *p;
    tree *temp=new tree;
    p=t;
    init(s);
    while(p!=NULL||s->top!=s->base)
    {
        if(p!=NULL)
        {
            cout<<p->data;
            push(s,p);
            p=p->lchild;
        }
        else
        {
            pop(s,temp);
            p=temp->rchild;
        }
    }
}
void inorder(tree *t)//非递归中序遍历
{
    stack *s=new stack;
    tree *p;
    init(s);
    p=t;
    tree *temp=new tree;
    while(p||s->top!=s->base)
    {
        if(p)
        {
               push(s,p);
               p=p->lchild;
        }
        else
        {
               pop(s,temp);
               cout<<temp->data;
               p=temp->rchild;
        }
    }
}
void postorder(tree *t)//非递归后序遍历
{
    int tag;
    stack *s=new stack;
    init(s);
    while(t!=NULL||s->top!=s->base)
    {
        while(t!=NULL)
        {
               t->tag=0;
               push(s,t);
               t=t->lchild;
        }
        t=new tree;
        while(s->top!=s->base&&(s->top-1)->tag==1)
        {
               pop(s,t);
               cout<<t->data;
        }
        if(s->top!=s->base)
        {
            (s->top-1)->tag=1;
               gettop(s,t);
               t=t->rchild;
        }
        else
            break;
    }
}
int main()
{
    tree *t;
    t = build();
    cout<<"非递归先序遍历"<<endl;
    preorder(t);
    cout<<endl;
    cout<<"非递归中序遍历"<<endl;
    inorder(t);
    cout<<endl;
    cout<<"非递归后续遍历"<<endl;
    postorder(t);
    cout<<endl;
    return 0;
}