(1)构造一棵二叉树，打印出前序遍历、中序遍历、后序遍历的遍历序列； (2)选择一种遍历方式计算该树中叶子结点的个数，并打印出叶子结点； (3)编写二叉树先序和中序非递归算法。用c++

在C++中，我们可以创建一个简单的二叉树结构，然后分别实现前序、中序和后序遍历，以及计算叶子节点数量的算法。以下是完整的代码：

#include <iostream>
using namespace std;

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

// 前序遍历
void preOrder(TreeNode* root) {
    if (root != nullptr) {
        cout << root->val << " ";
        preOrder(root->left);
        preOrder(root->right);
    }
}

// 中序遍历
void inOrder(TreeNode* root) {
    if (root != nullptr) {
        inOrder(root->left);
        cout << root->val << " ";
        inOrder(root->right);
    }
}

// 后序遍历
void postOrder(TreeNode* root) {
    if (root != nullptr) {
        postOrder(root->left);
        postOrder(root->right);
        cout << root->val << " ";
    }
}

// 计算叶子节点数量
int countLeaves(TreeNode* root) {
    if (root == nullptr) return 0;
    if (root->left == nullptr && root->right == nullptr) return 1;  // 如果左右都为空，则是一个叶子节点
    return countLeaves(root->left) + countLeaves(root->right);
}

int main() {
    // 构造二叉树示例
    TreeNode* root = new TreeNode(1);
    root->left = new TreeNode(2);
    root->right = new TreeNode(3);
    root->left->left = new TreeNode(4);
    root->left->right = new TreeNode(5);
    
    cout << "前序遍历: ";
    preOrder(root);
    cout << endl;

    cout << "中序遍历: ";
    inOrder(root);
    cout << endl;

    cout << "后序遍历: ";
    postOrder(root);
    cout << endl;

    cout << "叶子节点个数: " << countLeaves(root) << endl;

    delete root;
    return 0;
}