hdu_4547_CD操作(在线LCA)

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 }

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