解法：

#include<iostream>
using namespace std;
struct treeNode {
	char val;
	treeNode* left, * right;
	treeNode(char x) :val(x), left(NULL), right(NULL) {};
};
treeNode* buildtree() {
	char ch;
	cin >> ch;
	if (ch == '#') return NULL;
	treeNode* r = new treeNode(ch);
	r->left = buildtree();
	r->right = buildtree();
	return r;
}
void hdfs(treeNode* root) {
	if (root == NULL) return;
	hdfs(root->left);
	hdfs(root->right);
	swap(root->left, root->right);
	return;
}
void zdfs(treeNode* root) {
	if (root == NULL) return;
	zdfs(root->left);
	cout << root->val;
	zdfs(root->right);
	return;
}
void qdfs(treeNode* root) {
	if (root == NULL) return;
	cout << root->val;
	qdfs(root->left);
	qdfs(root->right);
	return;
}
int main() {
	treeNode* root = buildtree();
	hdfs(root);
	zdfs(root);
	cout << endl;
	qdfs(root);
	return 0;
}