求帮我看看为什么错误

#include<bits/stdc++.h>
using namespace std;
vector<char>nowp;
vector<char>ops;
vector<pair<char,char>>can;
vector<char>tmpvct;
int n;

void output()
{
	for (auto chr : nowp)
		cout << chr;
	cout << '\n';
}

void dfs()
{
	if (nowp.size() == n)
	{
		output();
		return;
	}

	for (char c : ops)
	{
		bool can_choose = true;
		if (find(nowp.begin(), nowp.end(), c) != nowp.end())
			continue;
		for (auto &p : can)
			if (p.second == c)
				if (find(nowp.begin(), nowp.end(), p.first) == nowp.end())
				{
					can_choose = false;
					break;
				}


		if (can_choose)
		{
			nowp.push_back(c);
			dfs();
			nowp.pop_back();
		}
	}
}

int main()
{
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	string tmp;
	while (getline(cin, tmp))
	{
		ops.clear();
		tmpvct.clear();
		nowp.clear();
		can.clear();
		stringstream ss;
		ss << tmp;
		char cr;
		while (ss >> cr)
			ops.emplace_back(cr);

		getline(cin, tmp);
		ss.clear();
		ss << tmp;
		while (ss >> cr)
			tmpvct.emplace_back(cr);
		for (int i = 0; i < tmpvct.size(); i += 2)
			can.emplace_back(tmpvct[i], tmpvct[i + 1]);
		sort(ops.begin(),ops.end());
		n = ops.size();
		dfs();
		cout << '\n';
	}
	return 0;
}