121 lines
1.9 KiB
C++
121 lines
1.9 KiB
C++
#include<cstdio>
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#include<cstring>
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using namespace std;
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struct node
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{
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int pos,st,step,pre;
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node(){}
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node(int _p,int _st,int _step)
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{
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pos=_p;
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st=_st;
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step=_step;
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}
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};
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bool had_answer,G[20][20],vis[20][1<<17];
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int n,m,s,t,res,head,tail,kase;
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node st;
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node que[20<<17];
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void init()
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{
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memset(&st,0,sizeof(st));
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memset(G,0,sizeof(G));
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memset(vis,0,sizeof(vis));
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head=tail=1;
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scanf("%d%d%d%d",&n,&m,&s,&t);
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int x,y;
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for(int i=0;i<m;i++)
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{
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scanf("%d",&x);
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st.st|=1<<x;
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}
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st.pos=s;
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st.st|=1<<s;
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for(int i=0;i<n-1;i++)
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{
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scanf("%d%d",&x,&y);
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G[x][y]=G[y][x]=1;
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}
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}
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int stk[10000],top;
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inline int lowbit(int n)
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{
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return n&(-n);
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}
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inline int count(int n)
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{
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int res=0;
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while(n)
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{
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res++;
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n>>=1;
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}
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return res;
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}
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void print(int n)
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{
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top=0;
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while(n!=0)
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{
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stk[top++]=que[n].st;
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n=que[n].pre;
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}
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while(top>1)
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{
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int x=stk[top-1]^stk[top-2],a=count(lowbit(x))-1,b=count(lowbit(x&~lowbit(x)))-1;
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if(stk[top-1]&1<<a) printf("%d %d\n",a,b);
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else printf("%d %d\n",b,a);
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top--;
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}
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}
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void solve()
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{
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if(s==t)
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{
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printf("Case %d: 0\n\n",++kase);
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return;
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}
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que[tail++]=st;
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vis[st.pos][st.st]=1;
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while(tail-head>0)
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{
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int st=que[head].st;
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for(int i=1;i<=n;i++)
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for(int j=1;j<=n;j++)
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if(i!=j&&G[i][j]&&((st&1<<i)>>i)&&!((st&1<<j)>>j))
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{
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que[tail].pos=(i==que[head].pos?j:que[head].pos);
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que[tail].pre=head;
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que[tail].step=que[head].step+1;
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que[tail].st=(st&(~(1<<i)))|1<<j;
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if(vis[que[tail].pos][que[tail].st]) continue;
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vis[que[tail].pos][que[tail].st]=1;
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if(que[tail].pos==t)
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{
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printf("Case %d: %d\n",++kase,que[tail].step);
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print(tail);
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printf("\n");
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return;
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}
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tail++;
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}
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head++;
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}
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printf("Case %d: -1\n\n",++kase);
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}
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int main()
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{
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// printf("%d %d %d\n",count(0),count(1),count(2));return 0;
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#ifdef local
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freopen("pro.in","r",stdin);
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#endif
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int t,kase=0;
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scanf("%d",&t);
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while(t-->0)
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{
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init();
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solve();
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}
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return 0;
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}
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