题目连接:http://acm.hdu.edu.cn/showproblem.php?pid=4547
题意:中文,不解释
题解:很裸的LCA,注意父目录打开子目录一次就够了,这里我才用倍增在线LCA+map过
1 #include<cstdio> 2 #include<iostream> 3 #include<map> 4 #include<string> 5 #define F(i,a,b) for(int i=a;i<=b;i++) 6 #pragma comment(linker, "/STACK:1024000000,1024000000") 7 using namespace std; 8 map<string,int>cnt; 9 const int N=1e5+5,DEG=18; 10 int t,n,m,a,b,ed,g[N],nxt[N],v[N],w[N],fa[N][DEG],dep[N],idx; 11 bool fg[N]; 12 string s1,s2; 13 inline void adg(int x,int y){v[++ed]=y,nxt[ed]=g[x],g[x]=ed;} 14 15 int Abs(int a){return a>0?a:-a;} 16 void dfs(int u,int pre){ 17 dep[u]=dep[pre]+1,fa[u][0]=pre; 18 F(i,1,DEG-1)fa[u][i]=fa[fa[u][i-1]][i-1]; 19 for(int i=g[u];~i;i=nxt[i])if(v[i]!=pre)dfs(v[i],u); 20 } 21 22 int LCA(int a,int b){ 23 if(dep[a]>dep[b])a^=b,b^=a,a^=b; 24 if(dep[a]<dep[b])F(i,0,DEG-1)if((dep[b]-dep[a])&(1<<i))b=fa[b][i]; 25 if(a!=b)for(int i=DEG-1;i<0?a=fa[a][0]:0,i>=0;i--) 26 if(fa[a][i]!=fa[b][i])a=fa[a][i],b=fa[b][i]; 27 return a; 28 } 29 30 int main(){ 31 scanf("%d",&t); 32 while(t--){ 33 scanf("%d%d",&n,&m); 34 cnt.clear(); 35 F(i,1,n)g[i]=-1,fg[i]=0;ed=0,idx=1; 36 F(i,1,n-1){ 37 cin>>s1>>s2; 38 a=cnt[s1],cnt[s1]=(a==0)?idx++:a,a=(a==0?idx-1:a); 39 b=cnt[s2],cnt[s2]=(b==0)?idx++:b,b=(b==0?idx-1:b); 40 adg(b,a),fg[a]=1; 41 } 42 int root; 43 F(i,1,n)if(!fg[i]){root=i;break;} 44 dep[root]=0; 45 dfs(root,root); 46 F(i,1,m){ 47 cin>>s1>>s2; 48 a=cnt[s1],b=cnt[s2]; 49 int lca=LCA(a,b),ans=0; 50 if(lca==a&&lca!=b)ans=1; 51 else if(lca==b&&lca!=a)ans=Abs(dep[a]-dep[b]); 52 else if(lca!=a&&lca!=b)ans=Abs(dep[a]-dep[lca])+1; 53 printf("%d ",ans); 54 } 55 } 56 return 0; 57 }