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楼主的代码：
```cpp
#include<iostream>
#include<cstdio>
#include<functional>
#include<cstring>
#include<string>
#include<queue>
#include<algorithm>
using namespace std;
string s1[6],s2[6];
int n = 1;//n个规则
int bfs(string a, string b) {
queue<string> q;
queue<string> q1;
int step = 0;
q.push(a);
while (step!=10) {
int flag = 1;
while (!q.empty()) {
string st = q.front();
q.pop();
if (st == b) {
cout << step;
return 0;
}
for (int i = 1; i <= n; i++) {
string str = st;
int bpos = 0;
while (str.find(s1[i], bpos) != -1) {
int post = str.find(s1[i], bpos);
bpos = post + 1;
flag = 0;
str.erase(post, s1[i].length());
str.insert(post, s2[i]);
q1.push(str);
str = st;
}
}
}
if (flag) {
cout << "NO ANSWER!";
return 0;
}
step++;
q.swap(q1);
}
}
int main() {
string a, b;
cin >> a >> b;
while (cin >> s1[n] >> s2[n]) n++;
n--;
bfs(a,b);
return 0;
}
```
by agicy @ 2018-08-14 16:47:51
```cpp
#include<iostream>
#include<cstdio>
#include<functional>
#include<cstring>
#include<string>
#include<queue>
#include<algorithm>
using namespace std;
string s1[6],s2[6];
int n = 1;//n个规则
int bfs(string a, string b)
{
queue<string> q;
queue<string> q1;
int step = 0;
q.push(a);
while (step!=10)
{
int flag = 1;
while (!q.empty())
{
string st = q.front();
q.pop();
if (st == b)
{
cout << step;
return 0;
}
for (int i = 1;i <= n;i++)
{
string str = st;
int bpos = 0;
while (str.find(s1[i], bpos) != -1)
{
int post = str.find(s1[i], bpos);
bpos = post + 1;
flag = 0;
str.erase(post, s1[i].length());
str.insert(post, s2[i]);
q1.push(str);
str = st;
}
}
}
if (flag)
{
cout << "NO ANSWER!";
return 0;
}
step++;
q.swap(q1);
}
}
int main()
{
string a, b;
cin >> a >> b;
while (cin >> s1[n] >> s2[n])
n++;
n--;
bfs(a,b);
return 0;
}
```
by 可乐配代码 @ 2018-08-14 16:48:17
@[可乐配代码](/space/show?uid=98040) 好像把`q.swap(q1);`改成`swap(q,q1);`就可以了。
by agicy @ 2018-08-14 16:50:19