P1032 [NOIP2002 提高组] 字串变换，仅代码

本喵今天累了，所以水一篇。
题目链接：link，请点击这里喵~

#include <stdio.h>
#include <ctype.h>
#include <algorithm>
#include <string>
#include <iostream>
#include <map>
#include <list>
#define lnt long long
#define inf 0x7fffffff
using namespace std;
int xx;char ff,chh;inline int read(){xx=ff=0;while(!isdigit(chh)){if(chh=='-'){ff=1;}chh=getchar();}while(isdigit(chh)){xx=(xx<<1)+(xx<<3)+chh-'0';chh=getchar();}return ff? -xx: xx;
}
const int N=50;
struct node{string x;int cnt;
};
map<string,bool> ys;
string to[N][2];
int main(){string a,b;list<node> q;cin>>a>>b;int m=0;while(cin>>to[m][0]>>to[m][1]){++m;}q.push_back({a,0});while(!q.empty()){node u=q.front();if(u.cnt>10){puts("NO ANSWER!");return 0;}if(u.x==b){printf("%d",u.cnt);return 0;}q.pop_front();string p=u.x;for(int i=0;i<m;++i){int e=0;while((e=u.x.find(to[i][0],e))!=string::npos){p=u.x;p.replace(e,to[i][0].length(),to[i][1]);++e;if(ys.find(p)!=ys.end()){continue;}ys[p]=1;q.push_back({p,u.cnt+1});}}}puts("NO ANSWER!");return 0;
}