【遍历二叉树】12往二叉树中添加层次链表的信息【Populating Next Right Pointers in Each Node II】

2023-01-07 20:46:03

本质上是二叉树的层次遍历，遍历层次的过程当中把next指针加上去。

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

和问题"Populating Next Right Pointers in Each Node"类似。

如果给定的树是任意的二叉树，你先前的方法还能工作吗？

笔记：

你只能用常量的辅助空间。

例如给定的是羡慕的二叉树，

当调用完你的函数后，这个树应该看起来想这样子：

         1 -> NULL

       /  \

      2 -> 3 -> NULL

     / \    \

    4-> 5 -> 7 -> NULL

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Follow up for problem "Populating Next Right Pointers in Each Node".

What if the given tree could be any binary tree? Would your previous solution still work?

Note:

You may only use constant extra space.

For example,
Given the following binary tree,

After calling your function, the tree should look like:

         1 -> NULL

       /  \

      2 -> 3 -> NULL

     / \    \

    4-> 5 -> 7 -> NULL

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

test.cpp：

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#include <iostream>
#include <cstdio>
#include <stack>
#include <vector>
#include "BinaryTreeWithNext.h"

using namespace std;

/**
* Definition for binary tree with next pointer.
* struct TreeLinkNode {
*  int val;
*  TreeLinkNode *left, *right, *next;
*  TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
* };
*/
void connect(TreeLinkNode *root)
{
    if(root == NULL)
    {
        return ;
    }
    vector<TreeLinkNode *> vec;
    vec.push_back(root);
    int count = 1;
    while(!vec.empty())
    {
        if(count > 1)
        {
            vec[0]->next = vec[1];
        }
        else
        {
            vec[0]->next = NULL;
        }

        if(vec[0]->left != NULL)
        {
            vec.push_back(vec[0]->left);
        }
        if(vec[0]->right != NULL)
        {
            vec.push_back(vec[0]->right);
        }

vec.erase(vec.begin());
count--;

if(count == 0)
        {
            count = vec.size();
        }
    }
}

// 树中结点含有分叉，
//                  1
//              /       \
//             2         3
//           /   \         \
//          4     5         7
int main()
{
    TreeLinkNode *pNodeA1 = CreateBinaryTreeNode(1);
    TreeLinkNode *pNodeA2 = CreateBinaryTreeNode(2);
    TreeLinkNode *pNodeA3 = CreateBinaryTreeNode(3);
    TreeLinkNode *pNodeA4 = CreateBinaryTreeNode(4);
    TreeLinkNode *pNodeA5 = CreateBinaryTreeNode(5);
    TreeLinkNode *pNodeA6 = CreateBinaryTreeNode(7);

ConnectTreeNodes(pNodeA1, pNodeA2, pNodeA3);
ConnectTreeNodes(pNodeA2, pNodeA4, pNodeA5);
ConnectTreeNodes(pNodeA3, NULL, pNodeA6);

connect(pNodeA1);

TreeLinkNode *trav = pNodeA1;
    TreeLinkNode *tmp;
    while (trav != NULL)
    {
        tmp = trav;
        while(tmp)
        {
            cout << tmp->val << " ";
            tmp = tmp->next;
        }
        cout << endl;
        trav = trav->left;
    }
    cout << endl;

DestroyTree(pNodeA1);
return 0;
}

结果输出：

2 3

4 5 7

BinaryTreeWithNext.h：

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#ifndef _BINARY_TREE_WITH_NEXT_H_
#define _BINARY_TREE_WITH_NEXT_H_

struct TreeLinkNode
{
    int val;
    TreeLinkNode *left;
    TreeLinkNode *right;
    TreeLinkNode *next;
    TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
};

TreeLinkNode *CreateBinaryTreeNode(int value);
void ConnectTreeNodes(TreeLinkNode *pParent,
TreeLinkNode *pLeft, TreeLinkNode *pRight);
void PrintTreeNode(TreeLinkNode *pNode);
void PrintTree(TreeLinkNode *pRoot);
void DestroyTree(TreeLinkNode *pRoot);

#endif /*_BINARY_TREE_WITH_NEXT_H_*/

BinaryTreeWithNext.cpp：

#include <iostream>
#include <cstdio>
#include "BinaryTreeWithNext.h"

using namespace std;

return pNode;
}

//连接结点
void ConnectTreeNodes(TreeLinkNode *pParent, TreeLinkNode *pLeft, TreeLinkNode *pRight)
{
    if(pParent != NULL)
    {
        pParent->left = pLeft;
        pParent->right = pRight;
    }
}

//打印节点内容以及左右子结点内容
void PrintTreeNode(TreeLinkNode *pNode)
{
    if(pNode != NULL)
    {
        printf("value of this node is: %d\n", pNode->val);

if(pNode->left != NULL)
            printf("value of its left child is: %d.\n", pNode->left->val);
        else
            printf("left child is null.\n");

if(pNode->right != NULL)
            printf("value of its right child is: %d.\n", pNode->right->val);
        else
            printf("right child is null.\n");
    }
    else
    {
        printf("this node is null.\n");
    }

printf("\n");
}

//前序遍历递归方法打印结点内容
void PrintTree(TreeLinkNode *pRoot)
{
PrintTreeNode(pRoot);

if(pRoot != NULL)
    {
        if(pRoot->left != NULL)
            PrintTree(pRoot->left);

if(pRoot->right != NULL)
PrintTree(pRoot->right);
}
}

void DestroyTree(TreeLinkNode *pRoot)
{
    if(pRoot != NULL)
    {
        TreeLinkNode *pLeft = pRoot->left;
        TreeLinkNode *pRight = pRoot->right;

delete pRoot;
pRoot = NULL;

DestroyTree(pLeft);
DestroyTree(pRight);
}
}

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