已知前序、中序遍历，求后序遍历

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
using namespace std;
void built(string a,string b,int length)
{
	if(length==0)
		return;
	int index;
	for(int i=0;i<b.length();i++)
	{
		if(a[0]==b[i])
		{
			index=i;
			break;
		}
	}
	string part1(a,1,index),part2(b,0,index);
	built(part1,part2,index);
	string part3(a,index+1,length-1),part4(b,index+1,length-1);
	built(part3,part4,length-1-index);
	cout<<a[0];
}
int main()
{
	string data1,data2;
	cin>>data1>>data2;
	int length=data1.length();
	built(data1,data2,length);
	return 0;
}

样例输入

ABDEFGCH
DFEGBAHC

样例输出

FGEDBHCA