【面试题019】二叉树的镜像

【面试题019】二叉树的镜像 

 

这道题很简单就是交换结点，利用递归解解决问题思路清晰，代码简洁；

MirrorTree.cpp:

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#include <iostream>
#include <cstdio>
#include <stack>
#include "BinaryTree.h"

using namespace std;

//递归
void MirrorRecursively(BinaryTreeNode *pNode)
{
    if((pNode == NULL) || (pNode->m_pLeft == NULL && pNode->m_pRight))
    {
        return ;
    }

    BinaryTreeNode *pTemp = pNode->m_pLeft;
    pNode->m_pLeft = pNode->m_pRight;
    pNode->m_pRight = pTemp;

    if(pNode->m_pLeft)
    {
        MirrorRecursively(pNode->m_pLeft);
    }
    if(pNode->m_pRight)
    {
        MirrorRecursively(pNode->m_pRight);
    }
}
//迭代
void MirrorIteratively(BinaryTreeNode *pRoot)
{
    if(pRoot == NULL)
    {
        return ;
    }

    stack<BinaryTreeNode *> stackTreeNode;
    stackTreeNode.push(pRoot);

    while(stackTreeNode.size() > 0)
    {
        BinaryTreeNode *pNode = stackTreeNode.top();
        stackTreeNode.pop();

        BinaryTreeNode *pTemp = pNode->m_pLeft;
        pNode->m_pLeft = pNode->m_pRight;
        pNode->m_pRight = pTemp;

        if(pNode->m_pLeft)
        {
            stackTreeNode.push(pNode->m_pLeft);
        }
        if(pNode->m_pRight)
        {
            stackTreeNode.push(pNode->m_pRight);
        }
    }
}

// ====================测试代码====================
// 测试完全二叉树：除了叶子节点，其他节点都有两个子节点
//            8
//        6      10
//       5 7    9  11
int main()
{
    printf("=====Test1 starts:===== ");
    BinaryTreeNode *pNode8 = CreateBinaryTreeNode(8);
    BinaryTreeNode *pNode6 = CreateBinaryTreeNode(6);
    BinaryTreeNode *pNode10 = CreateBinaryTreeNode(10);
    BinaryTreeNode *pNode5 = CreateBinaryTreeNode(5);
    BinaryTreeNode *pNode7 = CreateBinaryTreeNode(7);
    BinaryTreeNode *pNode9 = CreateBinaryTreeNode(9);
    BinaryTreeNode *pNode11 = CreateBinaryTreeNode(11);

    ConnectTreeNodes(pNode8, pNode6, pNode10);
    ConnectTreeNodes(pNode6, pNode5, pNode7);
    ConnectTreeNodes(pNode10, pNode9, pNode11);

    PrintTree(pNode8);

    printf("=====Test1: MirrorRecursively===== ");
    MirrorRecursively(pNode8);
    PrintTree(pNode8);

    printf("=====Test1: MirrorIteratively===== ");
    MirrorIteratively(pNode8);
    PrintTree(pNode8);

    DestroyTree(pNode8);
    return 0;
}

BinaryTree.h:

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#ifndef _BINARY_TREE_H_
#define _BINARY_TREE_H_

struct BinaryTreeNode
{
    int                    m_nValue;
    BinaryTreeNode        *m_pLeft;
    BinaryTreeNode        *m_pRight;
};

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


#endif /*_BINARY_TREE_H_*/

 

BinaryTree.cpp:

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

using namespace std;
BinaryTreeNode *CreateBinaryTreeNode(int value)
{
    BinaryTreeNode *pNode = new BinaryTreeNode();
    pNode->m_nValue = value;
    pNode->m_pLeft = NULL;
    pNode->m_pRight = NULL;

    return pNode;
}

void ConnectTreeNodes(
    BinaryTreeNode *pParent,
    BinaryTreeNode *pLeft,
    BinaryTreeNode *pRight)
{
    if(pParent != NULL)
    {
        pParent->m_pLeft = pLeft;
        pParent->m_pRight = pRight;
    }
}

void PrintTreeNode(BinaryTreeNode *pNode)
{
    if(pNode != NULL)
    {
        printf("value of this node is: %d ", pNode->m_nValue);

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

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

    printf(" ");
}

void PrintTree(BinaryTreeNode *pRoot)
{
    PrintTreeNode(pRoot);

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

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

void DestroyTree(BinaryTreeNode *pRoot)
{
    if(pRoot != NULL)
    {
        BinaryTreeNode *pLeft = pRoot->m_pLeft;
        BinaryTreeNode *pRight = pRoot->m_pRight;

        delete pRoot;
        pRoot = NULL;

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

Makefile:

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.PHONY:clean  
CPP=g++  
CFLAGS=-Wall -g  
BIN=test  
OBJS=MirrorTree.o BinaryTree.o  
LIBS=  
$(BIN):$(OBJS)  
    $(CPP) $(CFLAGS) $^ -o $@ $(LIBS)  
%.o:%.cpp  
    $(CPP) $(CFLAGS) -c $< -o $@  
clean:  
    rm -f *.o $(BIN)  



运行结果：

=====Test1 starts:=====
value of this node is: 8
value of its left child is: 6.
value of its right child is: 10.
value of this node is: 6
value of its left child is: 5.
value of its right child is: 7.
value of this node is: 5
left child is null.
right child is null.
value of this node is: 7
left child is null.
right child is null.
value of this node is: 10
value of its left child is: 9.
value of its right child is: 11.
value of this node is: 9
left child is null.
right child is null.
value of this node is: 11
left child is null.
right child is null.
=====Test1: MirrorRecursively=====
value of this node is: 8
value of its left child is: 10.
value of its right child is: 6.
value of this node is: 10
value of its left child is: 11.
value of its right child is: 9.
value of this node is: 11
left child is null.
right child is null.
value of this node is: 9
left child is null.
right child is null.
value of this node is: 6
value of its left child is: 7.
value of its right child is: 5.
value of this node is: 7
left child is null.
right child is null.
value of this node is: 5
left child is null.
right child is null.
=====Test1: MirrorIteratively=====
value of this node is: 8
value of its left child is: 6.
value of its right child is: 10.
value of this node is: 6
value of its left child is: 5.
value of its right child is: 7.
value of this node is: 5
left child is null.
right child is null.
value of this node is: 7
left child is null.
right child is null.
value of this node is: 10
value of its left child is: 9.
value of its right child is: 11.
value of this node is: 9
left child is null.
right child is null.
value of this node is: 11
left child is null.
right child is null.
 
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原文地址：https://www.cnblogs.com/codemylife/p/3715765.html