Codevs 1036 商务旅行
1 #include<cstdio> 2 #include<cmath> 3 #include<algorithm> 4 using namespace std; 5 const int maxn=100010; 6 int n,m,x,y,ans=0,tot=0,last[maxn],dep[maxn],p[maxn][32]; 7 struct edge{ 8 int to,pre; 9 }e[maxn<<1]; 10 11 void read(int &k){ 12 k=0; int f=1; char c=getchar(); 13 while (c<'0'||c>'9')c=='-'&&(f=-1),c=getchar(); 14 while ('0'<=c&&c<='9')k=k*10+c-'0',c=getchar(); 15 k*=f; 16 } 17 void add(int x,int y){ 18 e[++tot].to=y; 19 e[tot].pre=last[x]; 20 last[x]=tot; 21 } 22 void dfs(int u,int fa){ 23 dep[u]=dep[fa]+1; p[u][0]=fa; 24 for (int i=1;i<=log2(dep[u]);i++) p[u][i]=p[p[u][i-1]][i-1]; 25 for (int i=last[u],to=e[i].to;i;i=e[i].pre,to=e[i].to) 26 if (to!=fa) dfs(to,u); 27 } 28 int lca(int x,int y){ 29 if (dep[x]<dep[y]) swap(x,y); 30 if (dep[x]>dep[y]) 31 for (int i=log2(dep[x]-dep[y]+1);i>=0,dep[x]!=dep[y];i--) 32 if (dep[p[x][i]]>=dep[y]) x=p[x][i]; 33 if (x==y) return x; 34 for (int i=log2(dep[x]);i>=0;i--) 35 if (p[x][i]!=p[y][i]) x=p[x][i],y=p[y][i]; 36 return p[x][0]; 37 } 38 int main(){ 39 read(n); 40 for (int i=1;i<n;i++){ 41 read(x); read(y); 42 add(x,y); add(y,x); 43 } 44 dfs(1,0); 45 read(m); read(x); 46 for (int i=1;i<m;i++){ 47 read(y); 48 ans+=dep[x]+dep[y]-(dep[lca(x,y)]<<1); 49 x=y; 50 } 51 printf("%d ",ans); 52 return 0; 53 }