二叉树的先序、中序和后序遍历

#include 
using namespace std;

//树节点定义
struct Node {
    int val;
    Node *lchild;
    Node *rchild;

    Node(int x) : val(x), lchild(), rchild() {}
};

//先序遍历
void preOrder(Node *root) {
    if (root == nullptr) 
        return ;

    cout << root->val << endl;
    preOrder(root->lchild);
    preOrder(root->rchild);
}

//中序遍历
void inOrder(Node *root) {
    if (root == nullptr) 
        return ;
    inOrder(root->lchild);
    cout << root->val << endl;
    inOrder(root->rchild);
}

//后序遍历
void postOrder(Node *root) {
    if (root == nullptr) 
        return ;

    postOrder(root->lchild);
    postOrder(root->rchild);
    cout << root->val << endl;
}


int main() {
    Node *root = new Node(1);
    root->lchild = new Node(2);
    root->rchild = new Node(3);

    root->lchild->lchild = new Node(4);
    root->lchild->rchild = new Node(5);

    root->rchild->lchild = new Node(6);
    root->rchild->rchild = new Node(7);

    preOrder(root);
    cout << "==============" << endl;
    inOrder(root);
    cout << "==============" << endl;
    postOrder(root);
    cout << "==============" << endl;
    return 0;
}