[NOIP2002] 字串变换 宽搜+深度优化

#include <map>
#include <cstdio>
#include <string>
#include <vector>
#include <iostream>
namespace Hash{
  const int P=10000007;
  const int K=133;
  bool hash[10000007];
  inline int Hash(std::string s){
    int len=s.size(),ret=0;
    for(int i=0;i<len;i++)
      ret=(ret*K%P+s[i])%P;
    return ret;
  }
  inline bool ex(std::string s){
    return hash[Hash(s)];
  }
}
using namespace std;
vector<string> temp,now;
string a,b,stage[10][2];
int t;
map<string,bool> just;
int main(){
  freopen("string.in","r",stdin);
  freopen("string.out","w",stdout);
  cin>>a>>b;
  while(cin>>stage[++t][0])
    cin>>stage[t][1];
  t--;
  now.push_back(a);
  for(int k=1;k<=10;k++){
    temp.clear();
    for(int i=0;i<now.size();i++)
      for(int j=1;j<=t;j++)
        if(now[i].find(stage[j][0],0)!=string::npos){
          int pos=0;
          while(now[i].find(stage[j][0],pos)!=string::npos){
            string s=now[i];
            pos=now[i].find(stage[j][0],pos);
            s=s.replace(pos,stage[j][0].size(),stage[j][1]);
            if(Hash::ex(s)==0){
              Hash::hash[Hash::Hash(s)]=1;
              if(s==b){
                printf("%d",k);
                return 0;
              }
              temp.push_back(s);
            }
            pos+=stage[j][0].size();
          }
        }
    now=temp;
  }
  printf("NO ANSWER!");
  return 0;
}