c++二叉树的前，中，后序遍历实现

              1
           2     3
        4   5  6  7

本文主要实现了一个二叉树（c++），并且通过迭代的方式，实现了二叉树的前序遍历，中序遍历，后续遍历。

前序遍历：pre_order:
1 2 4 5 3 6 7
中序遍历：in_order:
4 2 5 1 6 3 7
后序遍历：post_order:
4 5 2 6 7 3 1

• 定义树

class binaryTree {
    public:
    int value;
    binaryTree* left;
    binaryTree* right;
    binaryTree() = default;
    binaryTree(int v):value(v) {
        left = right = nullptr;
    }
    ~binaryTree() {
        delete this->left;
        delete this->right;
        left = left = nullptr;
    }
};

• 构建树

binaryTree* buildTree() {
    //           1
    //        2     3
    //     4   5  6  7
    binaryTree* d = new binaryTree(1);
    d->left = new binaryTree(2);
    d->right = new binaryTree(3);

    d->left->left = new binaryTree(4);
    d->left->right = new binaryTree(5);

    d->right->left = new binaryTree(6);
    d->right->right = new binaryTree(7);
    return d;
}

• 前序遍历

void pre_order(const binaryTree* b) {
    if(b == nullptr) {
        return;
    }
    cout << b->value << " ";;
    pre_order(b->left);
    pre_order(b->right);
}
// output:
/*
preorder:
1 2 4 5 3 6 7 
*/

• 测试代码

void printTree() {
    binaryTree* b = buildTree();
    cout << "pre_order:" << endl;
    pre_order(b);
    cout << endl;

    cout << "in_order:" << endl;
    in_order(b);
    cout << endl;

    cout << "post_order:" << endl;
    post_order(b);
    cout << endl;
    return;
}

GitHub代码链接