蒟蒻调成这样也没过：

#include <iostream>
#include <string>
#include <map>
#include <unordered_map>
#include <queue>
#define s std::string
#define p std::pair<s,int>

s a[7][2];
int n,ans = 0x3f3f3f3f;
std::unordered_map<std::string,int> m1,m2;

size_t check(s x,s y,size_t pre)
{
    return x.find(y,pre);
}

s change(s x,int i,int to,size_t pos)
{
    s s3 = x;
    s3.replace(pos,a[i][to].length(),a[i][(to+1)%2]);
    return s3;
}

int main()
{
    while(std::cin>>a[n][0]>>a[n][1]) n++;
    n-=1;
    std::queue<p> q;
    q.push({a[0][0],0});
    m1[a[0][0]] = 0;
    m2[a[0][1]] = 0;
    while(!q.empty())
    {
        p t = q.front();
        q.pop();
        int cnt = t.second;
        s ts = t.first;
        if(cnt>=10) continue;
        for(int i=1;i<=n;i++)
        {
            size_t pos = check(ts,a[i][0],0),pre = pos;
            while(pos != std::string::npos)
            {
                p u;
                u.first = change(ts,i,0,pos);
                u.second = cnt+1;
                if(m1[u.first])
                {
                    pos = check(ts,a[i][0],pre+1);
                    pre = pos;
                    continue;
                }
                m1[u.first] = u.second;
                q.push(u);
                pos = check(ts,a[i][0],pre+1);
                pre = pos;
            }
        }
    }
    q.push({a[0][1],0});
    while(!q.empty())
    {
        p t = q.front();
        q.pop();
        int cnt = t.second;
        s ts = t.first;
        if(m1[ts]) ans = std::min(ans,m1[ts]+m2[ts]);
        if(cnt>=10) continue;
        for(int i=1;i<=n;i++)
        {
            size_t pos = check(ts,a[i][1],0),pre = pos;
            while(pos != std::string::npos)
            {
                p u;
                u.first = change(ts,i,1,pos);
                u.second = cnt+1;
                if(m2[u.first])
                {
                    pos = check(ts,a[i][1],pre+1);
                    pre = pos;
                    continue;
                }
                m2[u.first] = u.second;
                q.push(u);
                pos = check(ts,a[i][1],pre+1);
                pre = pos;
            }
        }
    }
    if(ans > 10) std::cout << "NO ANSWER!";
    else std::cout << ans;
    return 0;
}
/*
abab baba
a b
b a
*/