【面试题018】树的子结构

【面试题018】树的子结构 

 

输入两个二叉树A,B，判断B是不是A的子结构，

 

SubTree.cpp:

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#include <iostream> #include <cstdio> #include "BinaryTree.h" using namespace std; bool HasSubtreeCore(BinaryTreeNode *pRoot1, BinaryTreeNode *pRoot2); bool DoesTree1HaveTree2(BinaryTreeNode *pRoot1, BinaryTreeNode *pRoot2); bool HasSubtree(BinaryTreeNode *pRoot1, BinaryTreeNode *pRoot2) {     bool result = false;     if(pRoot1 != NULL && pRoot2 != NULL)     {         if(pRoot1->m_nValue == pRoot2->m_nValue)             result = DoesTree1HaveTree2(pRoot1, pRoot2);         if(!result)             result = HasSubtree(pRoot1->m_pLeft, pRoot2);         if(!result)             result = HasSubtree(pRoot1->m_pRight, pRoot2);     }     return result; } bool DoesTree1HaveTree2(BinaryTreeNode *pRoot1, BinaryTreeNode *pRoot2) {     if(pRoot2 == NULL)         return true;     if(pRoot1 == NULL)         return false;     if(pRoot1->m_nValue != pRoot2->m_nValue)         return false;     return DoesTree1HaveTree2(pRoot1->m_pLeft, pRoot2->m_pLeft) &&            DoesTree1HaveTree2(pRoot1->m_pRight, pRoot2->m_pRight); } // 树中结点含有分叉，树B是树A的子结构 //                  8                8 //              /                  /  //             8         7         9   2 //           /    //          9     2 //               /  //              4   7 int main() {     BinaryTreeNode *pNodeA1 = CreateBinaryTreeNode(8);     BinaryTreeNode *pNodeA2 = CreateBinaryTreeNode(8);     BinaryTreeNode *pNodeA3 = CreateBinaryTreeNode(7);     BinaryTreeNode *pNodeA4 = CreateBinaryTreeNode(9);     BinaryTreeNode *pNodeA5 = CreateBinaryTreeNode(2);     BinaryTreeNode *pNodeA6 = CreateBinaryTreeNode(4);     BinaryTreeNode *pNodeA7 = CreateBinaryTreeNode(7);     ConnectTreeNodes(pNodeA1, pNodeA2, pNodeA3);     ConnectTreeNodes(pNodeA2, pNodeA4, pNodeA5);     ConnectTreeNodes(pNodeA5, pNodeA6, pNodeA7);     BinaryTreeNode *pNodeB1 = CreateBinaryTreeNode(8);     BinaryTreeNode *pNodeB2 = CreateBinaryTreeNode(9);     BinaryTreeNode *pNodeB3 = CreateBinaryTreeNode(2);     ConnectTreeNodes(pNodeB1, pNodeB2, pNodeB3);     BinaryTreeNode *pRoot1 = pNodeA1;     BinaryTreeNode *pRoot2 = pNodeB1;     if(HasSubtree(pRoot1, pRoot2) == true)         printf("passed. ");     else         printf("failed. ");     DestroyTree(pNodeA1);     DestroyTree(pNodeB1);     return 0; }

运行结果：

passed.  

 

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=SubTree.o BinaryTree.o   LIBS=   $(BIN):$(OBJS)       $(CPP) $(CFLAGS) $^ -o $@ $(LIBS)   %.o:%.cpp       $(CPP) $(CFLAGS) -c $< -o $@   clean:       rm -f *.o $(BIN)