100 lines
2.9 KiB
C++
100 lines
2.9 KiB
C++
#include<iostream>
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#include<map>
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#include<string>
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#include<queue>
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using namespace std;
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bool is(string s)
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{
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int i,k=0,flag=0,t=0;
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int n=s.size();
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for(i=0;i<n;++i) {
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if(s[i]=='W'&&flag==1) k++;
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if(s[i]=='B') {
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flag=1;
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if(k!=0) {
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t=1;
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break;
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}
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}
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}
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if(t) return false;
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else return true;
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}
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int BFS(string s)
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{
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queue<string> Qu;
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int len=s.size(),f;
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string u,v;
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map<string,int> step;
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step[s]=0;
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Qu.push(s);
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while(!Qu.empty()) {
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u=Qu.front();
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Qu.pop();
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if(step[u]>=10) return -1;
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f=u.find('F');
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v=u;
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if(f+1<len) {
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v[f]=v[f+1];
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v[f+1]='F';
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if(step.find(v)==step.end()) {
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step[v]=step[u]+1;
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if(is(v)) return step[v];
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Qu.push(v);
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}
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}
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v=u;
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if(f-1>=0) {
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v[f]=v[f-1];
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v[f-1]='F';
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if(step.find(v)==step.end()) {
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step[v]=step[u]+1;
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if(is(v)) return step[v];
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Qu.push(v);
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}
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}
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v=u;
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if(f+2<len) {
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if(v[f+2]=='B')
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v[f]='W';
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if(v[f+2]=='W')
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v[f]='B';
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v[f+2]='F';
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if(step.find(v)==step.end()) {
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step[v]=step[u]+1;
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if(is(v)) return step[v];
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Qu.push(v);
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}
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}
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v=u;
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if(f-2>=0) {
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if(v[f-2]=='B')
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v[f]='W';
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if(v[f-2]=='W')
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v[f]='B';
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v[f-2]='F';
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if(step.find(v)==step.end()) {
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step[v]=step[u]+1;
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if(is(v)) return step[v];
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Qu.push(v);
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}
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}
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}
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return -1;
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}
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int main()
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{
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string state;
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int count=1,r;
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while(cin>>state)
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{
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if(state[0]=='-') break;
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if(is(state)) cout<<count++<<". 0"<<endl;
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else {
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r=BFS(state);
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r==-1?cout<<count++<<". -1"<<endl:cout<<count++<<". "<<r<<endl;
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}
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}
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return 0;
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}
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