二叉树的非递归遍历（后序遍历的经典解法）

最新推荐文章于 2024-05-29 16:57:33 发布

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本文介绍了一种使用栈实现二叉树前序、中序和后序遍历的方法，并通过具体的C++代码示例展示了如何构造二叉树并进行这三种遍历。

#include <iostream>
#include <stack>
using namespace std;

struct node
{
    int value;
    node* lchild;
    node* rchild;
};

void PreOrder(node* root)
{
    if(!root)
        return;
    stack<node*> view;

    while(!view.empty() || root)
    {
        while(root)
        {
            cout << root->value << " ";
            view.push(root);
            root = root->lchild;
        }
        root = view.top();
        view.pop();
        root = root->rchild;

    }
}

void InOrder(node* root)
{
    if(!root)
        return;
    stack<node*> view;
    while(!view.empty() || root)
    {
        while(root)
        {
            view.push(root);
            root = root->lchild;
        }
        root = view.top();
        cout << root->value << " ";
        view.pop();
        root = root->rchild;
    }
}

void PostOrder(node* root)
{
    if(!root)
        return;
    stack<node*> view;
    view.push(root);
    node* pre = NULL;
    while(!view.empty())
    {
        node* cur = view.top();

        if(((cur->lchild == pre || cur->rchild == pre) && pre) || (!cur->lchild && !cur->rchild))
        {
            cout << cur->value << " ";
            view.pop();
            pre = cur;
        }
        else
        {
            if(cur->rchild)
                view.push(cur->rchild);
            if(cur->lchild)
                view.push(cur->lchild);
        }
    }
}

int main()
{
    node* p1 = new node {6, NULL, NULL};
    node* p2 = new node {7, NULL, NULL};
    node* p3 = new node {4, p1, p2};
    node* p4 = new node {5, NULL, NULL};
    node* p5 = new node {3, p3, p4};

    cout << "preoder:";
    PreOrder(p5);
    cout << endl;

    cout << "inorder:";
    InOrder(p5);
    cout << endl;

    cout << "postorder:";
    PostOrder(p5);
    cout << endl;
    return 0;
}