代码：

#include <bits/stdc++.h>
using namespace std;

string a, b;
string A[10], B[10];
int cnt = 0;
struct node {
	string s;
	int t;
};
queue <node> q;
map <string, int> mp;

void bfs () {
	q.push ((node){a, 0});
	while (q.size()) {
		mp[q.front().s] ++;
		if (q.front().s == b) {
			if (q.front().t > 10) cout << "NO ANSWER!\n";
			else cout << q.front().t << endl;
			return ;
		}
		for (int i = 1; i <= cnt; i ++) {
			string tt = q.front().s;
			int p = 0;
			int c = 0;
			for (int j = 0; j < q.front().s.size(); j ++) {
				for (int k = j; k < q.front().s.size() && k - j + 1 <= A[i].size(); k ++) {
					if (q.front().s[k] == A[i][p]) {
						++ p;
					} else {
						break ;
					}
					if (p == A[i].size()) {
						tt.replace(k - p + 1, p, B[i]);
						if (mp[tt] == 0) q.push ((node){tt, q.front().t + (++ c)});
						
					}
				}
				p = 0;
			}
		}
		q.pop();
	}
	cout << "NO ANSWER!\n";
}

int main() {
	ios :: sync_with_stdio();
	cin.tie(0);
	cout.tie(0);
	
	cin >> a >> b;
	string s1, s2;
	
	while (cin >> s1) {
		cin >> s2;
		A[++ cnt] = s1;
		B[cnt] = s2;
	}
	bfs ();
	
	return 0;
}

测试记录
请各位大佬帮忙