关于树的常见操作-C++面试

#include <iostream>
using namespace std;

//树的存储结构与设计
struct BitNode
{
    int data;
    BitNode* leftChild;
    BitNode* rightChild;
    BitNode()
    {
        leftChild = NULL;
        rightChild = NULL;
    }
    BitNode(int x) :data(x), leftChild(NULL), rightChild(NULL)
    {

    }
};
//树的先序遍历
void PreOrder(BitNode* T)
{
    if (T == NULL)
    {
        return;
    }
    cout << T->data;
    PreOrder(T->leftChild);
    PreOrder(T->rightChild);
    return;

}
//树的中序遍历
void InOrder(BitNode* T)
{
    if (T == NULL)
    {
        return;
    }
    InOrder(T->leftChild);
    cout << T->data;
    InOrder(T->rightChild);
    return;
}
//树的后序遍历
void PostOrder(BitNode* T)
{
    if (T == NULL)
    {
        return;
    }
    PostOrder(T->leftChild);
    PostOrder(T->rightChild);
    cout << T->data;
}
//求树的叶子结点个数
int sum = 0;
int CountLeafNum(BitNode* T)
{
    
    if (T == NULL)
    {
        return 0;
    }
    if (T->leftChild == NULL && T->rightChild == NULL)
    {
        sum++;
    }
    CountLeafNum(T->leftChild);
    CountLeafNum(T->rightChild);
    return sum;
}
//求树的叶子结点个数-两个参数
void CountLeafNum(BitNode* T, int* sum)
{
    if (T == NULL)
    {
        return;
    }
    if (T->leftChild == NULL && T->rightChild == NULL)
    {
        *sum = *sum + 1; //等价于(*sum)++
    }
    CountLeafNum(T->leftChild, sum);
    CountLeafNum(T->rightChild, sum);
}
//求树的深度
int DepthOfTree(BitNode* T)
{
    int depthLeft = 0;
    int depthRight = 0;
    int depth = 0;
    if (T == NULL)
        return 0;
    depthLeft = DepthOfTree(T->leftChild);
    depthRight = DepthOfTree(T->rightChild);
    depth = 1 + ((depthLeft >depthRight)? depthLeft : depthRight);
    return depth;
}
//复制二叉树--用递归的思想，必须先根据返回值，定义新的变量类型用于递归的返回值赋值
BitNode* Copy(BitNode* T)
{
    if (T == NULL)
    {
        return NULL;
    }
    //用的前序遍历思想
    BitNode* newTreeLeft = Copy(T->leftChild);
    BitNode* newTreeRight = Copy(T->rightChild);
    
    //建立一个结点
    BitNode* newNode = new BitNode();
    if (newNode == NULL)
    {
        return NULL;
    }
    newNode->data = T->data;
    newNode->leftChild = newTreeLeft;
    newNode->rightChild = newTreeRight;
    return newNode;
}
int main()
{
    BitNode nodeA(1);
    BitNode nodeB(2);
    BitNode nodeC(3);
    BitNode nodeD(4);
    BitNode nodeE(5);
    BitNode nodeF(6);

    nodeA.leftChild = &nodeB;
    nodeA.rightChild = &nodeC;
    nodeB.leftChild = &nodeD;
    nodeB.rightChild = &nodeE;
    nodeC.leftChild = &nodeF;

    //前序遍历二叉树
    cout << "前序遍历二叉树 " << ":";
    PreOrder(&nodeA);
    cout << endl; 
    //中序遍历二叉树
    cout << "中序遍历二叉树 " << ":";
    InOrder(&nodeA);
    cout << endl;
    //后序遍历二叉树
    cout << "后序遍历二叉树 " << ":";
    PostOrder(&nodeA);
    cout << endl;

    //树的结点个数
    int leafCount = CountLeafNum(&nodeA);
    cout << "树的结点个数:" << leafCount << endl;

    //树的深度
    int depth = DepthOfTree(&nodeA);
    cout << "树的深度:" << depth << endl;

    //赋值一棵树
    BitNode* newNode = Copy(&nodeA);
    //后序遍历二叉树
    cout << "后序遍历二叉树 " << ":";
    PostOrder(newNode);
    cout << endl;

    system("pause");
    return 0;
}