提交记录：

https://www.luogu.com.cn/record/154571015

提示错误：

Wrong Answer.wrong answer On line 1 column 7, read (ASCII 0), expected G.

但是我本地跑了第一个测试点没有错误

求助

#include<algorithm>
#include<iostream>
#include<utility>
#include<random>
#include<queue>
#include<cmath>
#include<stack>
#include<map>
#include<set>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pa;
const ll N = 1e6 + 10, MOD = 1e9 + 7, INF = 0x7fffffffffffffff;
ll t, n, m;
vector<char> ans;
ll indb = 0;
string a, b;
void dfs(int al,int ar) {
	if (al > ar)return;
	ll mid;
	for (int i = al; i <= ar; i++) {
		if (a[i] == b[indb]) {
			mid = i;
			break;
		}
	}
	ll tmp = indb;
	indb++;
	dfs(al, mid - 1);
	dfs(mid + 1, ar);
	ans.push_back(b[tmp]);
}
void solve() {
	cin >> a >> b;
	dfs(0, a.size());
	for (char i : ans)cout << i;
	//cout << '\n';
}
int main() {
	t = 1;
	//cin >> t;
	while (t--) {
		solve();
	}
}