中序后序求前序

#include<bits/stdc++.h>
//中序 后序 求前序
using namespace std;
void f2(string& pre, string in, string post) {
	if (post.length() == 0)//序列为空结束
		return;
	int n = post.length() - 1;//根节点
	char ch = post[n];
	pre += ch;//根节点存入前序中
	//处理左子树
	f2(pre, in.substr(0, in.find(ch)), post.substr(0, in.find(ch)));
	//处理右子树
	f2(pre, in.substr(in.find(ch) + 1, in.length() - in.find(ch) - 1), post.substr(in.find(ch), in.length() - in.find(ch) - 1));
}
int main() {
	string pre = "";//ABCDEF
	string in = "fcaegbd";//"CBAEDF";
	string post = "fcgedba";//"CBEFDA";
	f2(pre, in, post);
	cout << pre << endl;
}