根据先序和中序求后序，注意递归终止条件

#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
//根据先序和中序求后序
void LastOrd(string PreOrder, string MidOrder, int n)
{
	if (n == 0)
		return;
	if (n == 1)
	{
		cout << PreOrder[0];
		return;
	}
	size_t rootPos = MidOrder.find(PreOrder[0]);
	string subPreOrder1 = PreOrder.substr(1, rootPos);
	string subPreOrder2 = PreOrder.substr(1 + rootPos, string::npos);
	string subMinOrder1 = MidOrder.substr(0, rootPos);
	string subMinOrder2 = MidOrder.substr(rootPos + 1, string::npos);

	LastOrd(subPreOrder1, subMinOrder1, rootPos);
	LastOrd(subPreOrder2, subMinOrder2, n - rootPos - 1);
	cout << PreOrder[0];
}

int main()
{
	string PreOrder, MidOrder;
	while (cin >> PreOrder >> MidOrder)
	{
		LastOrd(PreOrder, MidOrder, PreOrder.size());
		cout << endl;
	}
	return 0;
}