全AC 的“病毒代码”

#include<bits/stdc++.h>
using namespace std;
string back, in;

int find(char ch){
	for(int i = 0; i < in.length(); i++){
		if(in[i] == ch)   return  i;
	}
}

void dfs(int back_start, int back_end, int in_start, int in_end){
	int root = find(back[back_end]);
	printf("%c", back[back_end]);
	if(root > in_start){
		dfs(back_start, back_end - (in_end - root + 1), in_start, root - 1);
	}
	if(root < in_end){
		dfs(root-in_start + 1, back_end - 1, root + 1, in_end);
	}
	return;
}

int main(){
	cin>>in>>back;
	int len = in.length();
	dfs(0, len - 1, 0, len - 1);
	
	return 0;
}