字串變換

 1 #include<iostream>
 2 #include<stdio.h>
 3 #include<set>
 4 #include<vector>
 5 #include<queue>
 6 #include<utility>
 7 #include<string>
 8 #include<stdlib.h>
 9 using namespace std;
10 struct data{string str;int step;};
11 vector<pair<string
 
,string> > v;
12 set<string> s;
13 string a,b,ta,tb,ts;
14 void Search(); 
15 int main()
16 {
17     cin>>a>>b;
18     while(cin>>ta>>tb)
19         v.push_back(make_pair(ta,tb));
20     Search(); 
21 }
22 void Search()
23 {
24     data f,p;
25     p.str=a;
 
26     p.step=0;
27     queue<data> q;
28     q.push(p);
29     while(!q.empty())
30     {
31         f=q.front();
32         if(f.step>10)
33         {
34             printf("NO ANSWER!");
35             exit(0); 
36         }
37         for(int i=0;i<v.size();++i)
38         {
 
39             if(f.str.find(v[i].first)!=-1)
40             {
41                 for(int j=f.str.find(v[i].first);j<f.str.length();j=f.str.find(v[i].first,j+1))
42                 {
43                     ts=f.str;
44                     ts.replace(j,v[i].first.length(),v[i].second);
45                     if(ts==b)
46                     {
47                         printf("%d",f.step+1);
48                         exit(0);
49                     }
50                     if(!s.count(ts))
51                     {
52                         s.insert(ts);
53                         p.step=f.step+1;
54                         p.str=ts;
55                         q.push(p);
56                     }
57                 }
58             }
59         }
60         q.pop();
61     }
62     printf("NO ANSWER!");
63     exit(0);
64 }

[NOIp2002]字串變換