面试题19—二叉树的镜像

题目：输入一个二叉树，输出它的镜像。

代码示例：

头文件：BinaryTree.h

#pragma once#include<iostream>#include <stack>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);void MirrorRecursively(BinaryTreeNode *pNode);void MirrorIteratively(BinaryTreeNode* pRoot);

源文件：BinaryTree.cpp

#include "BinaryTree.h"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\n", pNode->m_nValue);if (pNode->m_pLeft != NULL)printf("value of its left child is: %d.\n", pNode->m_pLeft->m_nValue);elseprintf("left child is null.\n");if (pNode->m_pRight != NULL)printf("value of its right child is: %d.\n", pNode->m_pRight->m_nValue);elseprintf("right child is null.\n");}else{printf("this node is null.\n");}printf("\n");}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);}}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);}void MirrorIteratively(BinaryTreeNode* pRoot){if (pRoot == NULL)return;std::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);}}

主函数：main.cpp

#include "BinaryTree.h"// ====================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  11void Test1(){printf("=====Test1 starts:=====\n");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=====\n");MirrorRecursively(pNode8);PrintTree(pNode8);printf("=====Test1: MirrorIteratively=====\n");MirrorIteratively(pNode8);PrintTree(pNode8);DestroyTree(pNode8);}// 测试二叉树：出叶子结点之外，左右的结点都有且只有一个左子结点//            8//          7   //        6 //      5//    4void Test2(){printf("=====Test2 starts:=====\n");BinaryTreeNode* pNode8 = CreateBinaryTreeNode(8);BinaryTreeNode* pNode7 = CreateBinaryTreeNode(7);BinaryTreeNode* pNode6 = CreateBinaryTreeNode(6);BinaryTreeNode* pNode5 = CreateBinaryTreeNode(5);BinaryTreeNode* pNode4 = CreateBinaryTreeNode(4);ConnectTreeNodes(pNode8, pNode7, NULL);ConnectTreeNodes(pNode7, pNode6, NULL);ConnectTreeNodes(pNode6, pNode5, NULL);ConnectTreeNodes(pNode5, pNode4, NULL);PrintTree(pNode8);printf("=====Test2: MirrorRecursively=====\n");MirrorRecursively(pNode8);PrintTree(pNode8);printf("=====Test2: MirrorIteratively=====\n");MirrorIteratively(pNode8);PrintTree(pNode8);DestroyTree(pNode8);}// 测试二叉树：出叶子结点之外，左右的结点都有且只有一个右子结点//            8//             7   //              6 //               5//                4void Test3(){printf("=====Test3 starts:=====\n");BinaryTreeNode* pNode8 = CreateBinaryTreeNode(8);BinaryTreeNode* pNode7 = CreateBinaryTreeNode(7);BinaryTreeNode* pNode6 = CreateBinaryTreeNode(6);BinaryTreeNode* pNode5 = CreateBinaryTreeNode(5);BinaryTreeNode* pNode4 = CreateBinaryTreeNode(4);ConnectTreeNodes(pNode8, NULL, pNode7);ConnectTreeNodes(pNode7, NULL, pNode6);ConnectTreeNodes(pNode6, NULL, pNode5);ConnectTreeNodes(pNode5, NULL, pNode4);PrintTree(pNode8);printf("=====Test3: MirrorRecursively=====\n");MirrorRecursively(pNode8);PrintTree(pNode8);printf("=====Test3: MirrorIteratively=====\n");MirrorIteratively(pNode8);PrintTree(pNode8);DestroyTree(pNode8);}// 测试空二叉树：根结点为空指针void Test4(){printf("=====Test4 starts:=====\n");BinaryTreeNode* pNode = NULL;PrintTree(pNode);printf("=====Test4: MirrorRecursively=====\n");MirrorRecursively(pNode);PrintTree(pNode);printf("=====Test4: MirrorIteratively=====\n");MirrorIteratively(pNode);PrintTree(pNode);}// 测试只有一个结点的二叉树void Test5(){printf("=====Test5 starts:=====\n");BinaryTreeNode* pNode8 = CreateBinaryTreeNode(8);PrintTree(pNode8);printf("=====Test4: MirrorRecursively=====\n");MirrorRecursively(pNode8);PrintTree(pNode8);printf("=====Test4: MirrorIteratively=====\n");MirrorIteratively(pNode8);PrintTree(pNode8);}int main(){Test1();/*Test2();Test3();Test4();Test5();*/return 0;}