剑指offer_面试题18_树的子结构

题目：输入两棵二叉树 A 和 B，判断 B 是不是 A 的子结构。

两个步骤：

1、第一步在树 A 中找到和树 B 的根结点的值一样的结点 R

2、第二步再判断树 A 中以 R 为根结点的子树是不是包含和树 B 一样的结构。

对于递归：想好判断条件，以及 什么条件下该去递归。

#include <iostream>#include <cstdlib>using namespace std;typedef struct node{    int m_pValue;    struct node *lchild;    struct node *rchild;}TreeNode;/**创建一个二叉树结点*/TreeNode * create_Treenode(int elem){    TreeNode *pRoot;    pRoot = new TreeNode;    pRoot->m_pValue = elem;    pRoot->lchild = NULL;    pRoot->rchild = NULL;    return pRoot;}/**将二叉树结点连接起来，组成一颗二叉树*/TreeNode * connect_Treenode(TreeNode *pRoot, TreeNode *p_lchild, TreeNode *p_rchild){    if(NULL == pRoot)        return pRoot;    pRoot->lchild = p_lchild;    pRoot->rchild = p_rchild;    return pRoot;}//TreeNode * delete_node()/**在根结点找到的情况下，判断树1中是否存在树2的结构*/bool Does_tree1_have_tree2(TreeNode *pRoot1,TreeNode *pRoot2){    if(pRoot2 == NULL)   /**在找的过程中，如果树2遍历到了叶节点，说明前面的节点都相同*/        return true;    if(pRoot1 == NULL)   /**树1遍历到叶结点，说明找不到树2中的结点*/        return false;    if(pRoot1->m_pValue != pRoot2->m_pValue)        return false;    return Does_tree1_have_tree2(pRoot1->lchild,pRoot2->lchild) &&        Does_tree1_have_tree2(pRoot1->rchild,pRoot2->rchild);}/**感觉写递归，就是想好一步应该判断的条件，什么情况下返回*//**找根结点*/bool Hassubtree(TreeNode *pRoot1,TreeNode *pRoot2){    bool result = false;    if(pRoot1 != NULL && pRoot2 != NULL)    {        if(pRoot1->m_pValue == pRoot2->m_pValue)            result = Does_tree1_have_tree2(pRoot1,pRoot2);        if(!result)                    /**如果根结点不是，那先去找左孩子*/            result = Hassubtree(pRoot1->lchild,pRoot2);        if(!result)                    /**如果左孩子还不是，那去找右孩子*/            result = Hassubtree(pRoot1->rchild,pRoot2);    }    return result;}/**测试函数，来源于书本，学习了这种测试函数写法，很有收获*/void Test(const char* testName, TreeNode* pRoot1, TreeNode* pRoot2, bool expected)   /**此处 testName 前应该加 const*/{    if(Hassubtree(pRoot1, pRoot2) == expected)        cout << testName << " passed." << endl;    else        cout << testName << " failed." << endl;}/** 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                    */void Test1(){    TreeNode* pNodeA1 = create_Treenode(8);    TreeNode* pNodeA2 = create_Treenode(8);    TreeNode* pNodeA3 = create_Treenode(7);    TreeNode* pNodeA4 = create_Treenode(9);    TreeNode* pNodeA5 = create_Treenode(2);    TreeNode* pNodeA6 = create_Treenode(4);    TreeNode* pNodeA7 = create_Treenode(7);    connect_Treenode(pNodeA1, pNodeA2, pNodeA3);    connect_Treenode(pNodeA2, pNodeA4, pNodeA5);    connect_Treenode(pNodeA5, pNodeA6, pNodeA7);    TreeNode* pNodeB1 = create_Treenode(8);    TreeNode* pNodeB2 = create_Treenode(9);    TreeNode* pNodeB3 = create_Treenode(2);    connect_Treenode(pNodeB1, pNodeB2, pNodeB3);    Test("Test1", pNodeA1, pNodeB1, true);    //DestroyTree(pNodeA1);    //DestroyTree(pNodeB1);}/** 树中结点含有分叉，树B不是树A的子结构*//**                  8                8   *//**              /       \           / \  *//**             8         7         9   2 *//**           /   \                       *//**          9     3                      *//**               / \                     *//**              4   7                    */void Test2(){    TreeNode* pNodeA1 = create_Treenode(8);    TreeNode* pNodeA2 = create_Treenode(8);    TreeNode* pNodeA3 = create_Treenode(7);    TreeNode* pNodeA4 = create_Treenode(9);    TreeNode* pNodeA5 = create_Treenode(3);    TreeNode* pNodeA6 = create_Treenode(4);    TreeNode* pNodeA7 = create_Treenode(7);    connect_Treenode(pNodeA1, pNodeA2, pNodeA3);    connect_Treenode(pNodeA2, pNodeA4, pNodeA5);    connect_Treenode(pNodeA5, pNodeA6, pNodeA7);    TreeNode* pNodeB1 = create_Treenode(8);    TreeNode* pNodeB2 = create_Treenode(9);    TreeNode* pNodeB3 = create_Treenode(2);    connect_Treenode(pNodeB1, pNodeB2, pNodeB3);    Test("Test2", pNodeA1, pNodeB1, false);    //DestroyTree(pNodeA1);    //DestroyTree(pNodeB1);}// 树中结点只有左子结点，树B是树A的子结构//                8                  8//              /                   ///             8                   9//           /                    ///          9                    2//         ///        2//       ///      5void Test3(){    TreeNode* pNodeA1 = create_Treenode(8);    TreeNode* pNodeA2 = create_Treenode(8);    TreeNode* pNodeA3 = create_Treenode(9);    TreeNode* pNodeA4 = create_Treenode(2);    TreeNode* pNodeA5 = create_Treenode(5);    connect_Treenode(pNodeA1, pNodeA2, NULL);    connect_Treenode(pNodeA2, pNodeA3, NULL);    connect_Treenode(pNodeA3, pNodeA4, NULL);    connect_Treenode(pNodeA4, pNodeA5, NULL);    TreeNode* pNodeB1 = create_Treenode(8);    TreeNode* pNodeB2 = create_Treenode(9);    TreeNode* pNodeB3 = create_Treenode(2);    connect_Treenode(pNodeB1, pNodeB2, NULL);    connect_Treenode(pNodeB2, pNodeB3, NULL);    Test("Test3", pNodeA1, pNodeB1, true);    //DestroyTree(pNodeA1);    //DestroyTree(pNodeB1);}// 树中结点只有左子结点，树B不是树A的子结构//                8                  8//              /                   ///             8                   9//           /                    ///          9                    3//         ///        2//       ///      5void Test4(){    TreeNode* pNodeA1 = create_Treenode(8);    TreeNode* pNodeA2 = create_Treenode(8);    TreeNode* pNodeA3 = create_Treenode(9);    TreeNode* pNodeA4 = create_Treenode(2);    TreeNode* pNodeA5 = create_Treenode(5);    connect_Treenode(pNodeA1, pNodeA2, NULL);    connect_Treenode(pNodeA2, pNodeA3, NULL);    connect_Treenode(pNodeA3, pNodeA4, NULL);    connect_Treenode(pNodeA4, pNodeA5, NULL);    TreeNode* pNodeB1 = create_Treenode(8);    TreeNode* pNodeB2 = create_Treenode(9);    TreeNode* pNodeB3 = create_Treenode(3);    connect_Treenode(pNodeB1, pNodeB2, NULL);    connect_Treenode(pNodeB2, pNodeB3, NULL);    Test("Test4", pNodeA1, pNodeB1, false);    //DestroyTree(pNodeA1);    //DestroyTree(pNodeB1);}// 树中结点只有右子结点，树B是树A的子结构//       8                   8//        \                   \//         8                   9//          \                   \//           9                   2//            \//             2//              \//               5void Test5(){    TreeNode* pNodeA1 = create_Treenode(8);    TreeNode* pNodeA2 = create_Treenode(8);    TreeNode* pNodeA3 = create_Treenode(9);    TreeNode* pNodeA4 = create_Treenode(2);    TreeNode* pNodeA5 = create_Treenode(5);    connect_Treenode(pNodeA1, NULL, pNodeA2);    connect_Treenode(pNodeA2, NULL, pNodeA3);    connect_Treenode(pNodeA3, NULL, pNodeA4);    connect_Treenode(pNodeA4, NULL, pNodeA5);    TreeNode* pNodeB1 = create_Treenode(8);    TreeNode* pNodeB2 = create_Treenode(9);    TreeNode* pNodeB3 = create_Treenode(2);    connect_Treenode(pNodeB1, NULL, pNodeB2);    connect_Treenode(pNodeB2, NULL, pNodeB3);    Test("Test5", pNodeA1, pNodeB1, true);    //DestroyTree(pNodeA1);    //DestroyTree(pNodeB1);}// 树A中结点只有右子结点，树B不是树A的子结构//       8                   8//        \                   \//         8                   9//          \                 / \//           9               3   2//            \//             2//              \//               5void Test6(){    TreeNode* pNodeA1 = create_Treenode(8);    TreeNode* pNodeA2 = create_Treenode(8);    TreeNode* pNodeA3 = create_Treenode(9);    TreeNode* pNodeA4 = create_Treenode(2);    TreeNode* pNodeA5 = create_Treenode(5);    connect_Treenode(pNodeA1, NULL, pNodeA2);    connect_Treenode(pNodeA2, NULL, pNodeA3);    connect_Treenode(pNodeA3, NULL, pNodeA4);    connect_Treenode(pNodeA4, NULL, pNodeA5);    TreeNode* pNodeB1 = create_Treenode(8);    TreeNode* pNodeB2 = create_Treenode(9);    TreeNode* pNodeB3 = create_Treenode(3);    TreeNode* pNodeB4 = create_Treenode(2);    connect_Treenode(pNodeB1, NULL, pNodeB2);    connect_Treenode(pNodeB2, pNodeB3, pNodeB4);    Test("Test6", pNodeA1, pNodeB1, false);    //DestroyTree(pNodeA1);    //DestroyTree(pNodeB1);}// 树A为空树void Test7(){    TreeNode* pNodeB1 = create_Treenode(8);    TreeNode* pNodeB2 = create_Treenode(9);    TreeNode* pNodeB3 = create_Treenode(3);    TreeNode* pNodeB4 = create_Treenode(2);    connect_Treenode(pNodeB1, NULL, pNodeB2);    connect_Treenode(pNodeB2, pNodeB3, pNodeB4);    Test("Test7", NULL, pNodeB1, false);    //DestroyTree(pNodeB1);}// 树B为空树void Test8(){    TreeNode* pNodeA1 = create_Treenode(8);    TreeNode* pNodeA2 = create_Treenode(9);    TreeNode* pNodeA3 = create_Treenode(3);    TreeNode* pNodeA4 = create_Treenode(2);    connect_Treenode(pNodeA1, NULL, pNodeA2);    connect_Treenode(pNodeA2, pNodeA3, pNodeA4);    Test("Test8", pNodeA1, NULL, false);    //DestroyTree(pNodeA1);}// 树A和树B都为空void Test9(){    Test("Test9", NULL, NULL, false);}int main(){    Test1();    Test2();    Test3();    Test4();    Test5();    Test6();    Test7();    Test8();    Test9();    return 0;}

/*点滴积累，我的一小步O(∩_∩)O~*/