《剑指offer》第五十四题（二叉搜索树的第k个结点）

// 面试题54：二叉搜索树的第k个结点
// 题目：给定一棵二叉搜索树，请找出其中的第k大的结点。

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

const BinaryTreeNode* KthNodeCore(const BinaryTreeNode* pRoot, unsigned int& k);

const BinaryTreeNode* KthNode(const BinaryTreeNode* pRoot, unsigned int k)
{
    if (pRoot == nullptr || k == )//判断边界
        return nullptr;

    return KthNodeCore(pRoot, k);
}

const BinaryTreeNode* KthNodeCore(const BinaryTreeNode* pRoot, unsigned int& k)//k必须引用传递啊，不然记不住
{
    const BinaryTreeNode* target = nullptr;

    if (pRoot->m_pLeft != nullptr)//迭代找出最小点
        target = KthNodeCore(pRoot->m_pLeft, k);

    if (target == nullptr)//找到最小节点了，并k--，如果k==1，就算是找到了，记下target
    {
        if (k == )
            target = pRoot;

        k--;
    }

    if (target == nullptr && pRoot->m_pRight != nullptr)//一旦找到target，就不会继续迭代了，全部返回
        target = KthNodeCore(pRoot->m_pRight, k);

    return target;
}

// ====================测试代码====================
void Test(const char* testName, const BinaryTreeNode* pRoot, unsigned int k, bool isNull, int expected)
{
    if (testName != nullptr)
        printf("%s begins: ", testName);

    const BinaryTreeNode* pTarget = KthNode(pRoot, k);
    if ((isNull && pTarget == nullptr) || (!isNull && pTarget->m_nValue == expected))
        printf("Passed.\n");
    else
        printf("FAILED.\n");
}

//            8
//        6      10
//       5 7    9  11
void TestA()
{
    BinaryTreeNode* pNode8 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode6 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode10 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode5 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode7 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode9 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode11 = CreateBinaryTreeNode();

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

    Test("TestA0", pNode8, , true, -);
    Test("TestA1", pNode8, , false, );
    Test("TestA2", pNode8, , false, );
    Test("TestA3", pNode8, , false, );
    Test("TestA4", pNode8, , false, );
    Test("TestA5", pNode8, , false, );
    Test("TestA6", pNode8, , false, );
    Test("TestA7", pNode8, , false, );
    Test("TestA8", pNode8, , true, -);

    DestroyTree(pNode8);

    printf("\n\n");
}

//               5
//              /
//             4
//            /
//           3
//          /
//         2
//        /
//
void TestB()
{
    BinaryTreeNode* pNode5 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode4 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode3 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode2 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode1 = CreateBinaryTreeNode();

    ConnectTreeNodes(pNode5, pNode4, nullptr);
    ConnectTreeNodes(pNode4, pNode3, nullptr);
    ConnectTreeNodes(pNode3, pNode2, nullptr);
    ConnectTreeNodes(pNode2, pNode1, nullptr);

    Test("TestB0", pNode5, , true, -);
    Test("TestB1", pNode5, , false, );
    Test("TestB2", pNode5, , false, );
    Test("TestB3", pNode5, , false, );
    Test("TestB4", pNode5, , false, );
    Test("TestB5", pNode5, , false, );
    Test("TestB6", pNode5, , true, -);

    DestroyTree(pNode5);

    printf("\n\n");
}

// 1
//  \
//   2
//    \
//     3
//      \
//       4
//        \
//
void TestC()
{
    BinaryTreeNode* pNode1 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode2 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode3 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode4 = CreateBinaryTreeNode();
    BinaryTreeNode* pNode5 = CreateBinaryTreeNode();

    ConnectTreeNodes(pNode1, nullptr, pNode2);
    ConnectTreeNodes(pNode2, nullptr, pNode3);
    ConnectTreeNodes(pNode3, nullptr, pNode4);
    ConnectTreeNodes(pNode4, nullptr, pNode5);

    Test("TestC0", pNode1, , true, -);
    Test("TestC1", pNode1, , false, );
    Test("TestC2", pNode1, , false, );
    Test("TestC3", pNode1, , false, );
    Test("TestC4", pNode1, , false, );
    Test("TestC5", pNode1, , false, );
    Test("TestC6", pNode1, , true, -);

    DestroyTree(pNode1);

    printf("\n\n");
}

// There is only one node in a tree
void TestD()
{
    BinaryTreeNode* pNode1 = CreateBinaryTreeNode();

    Test("TestD0", pNode1, , true, -);
    Test("TestD1", pNode1, , false, );
    Test("TestD2", pNode1, , true, -);

    DestroyTree(pNode1);

    printf("\n\n");
}

// empty tree
void TestE()
{
    Test("TestE0", nullptr, , true, -);
    Test("TestE1", nullptr, , true, -);

    printf("\n\n");
}

int main(int argc, char* argv[])
{
    TestA();
    TestB();
    TestC();
    TestD();
    TestE();

    system("pause");
}