Utopia [ZOJ 2838]

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=2838

//对于x,y,z树上的位置进行分类讨论
/*
    z         z      t       t
    /\        /      /\      /\
    x y        t        z  y    x  z
            /\      /           \
            x y     x            y
*/
const int MM = 55555;
int N, M;
vector<int>edge[MM];
bool vis[MM];
int dp[MM<<2][30];
int ief,level;
int E[MM<<2], L[MM<<2], H[MM<<2];


void get_data() {
    int i,j,k,x,y;
    for(i=0;i<MM;i++) edge[i].clear();
    for(i=1;i<N;i++) {
        scanf("%d%d",&x,&y);
        edge[x].push_back(y), edge[y].push_back(x);
    }
}
void dfs(int u) {
    int i,j,k,v;
    E[++ief]=u; H[u]=ief; L[ief]=++level;
    for(i=0;i<edge[u].size();i++) {
        v=edge[u][i];
        if(!vis[v]) {
            vis[v]=true; dfs(v); 
            E[++ief]=u; L[ief]=--level;
        }
    }
}
void init_rmq() {
    int i,j,k,lim;
    for(i=1;i<=ief;i++) dp[i][0]=i;
    k=(int)(log(1.0*ief)/log(2.0));
    for(i=1;i<=k;i++) {
        lim=ief-(1<<i)+1;
        for(j=1;j<=lim;j++) {
            if(L[dp[j][i-1]]>L[dp[j+(1<<(i-1))][i-1]])
                dp[j][i]=dp[j+(1<<(i-1))][i-1];
            else dp[j][i]=dp[j][i-1];
        }
    }
}
int query(int x,int y) {
    if(x>y) swap(x,y);
    int k=(int)(log(y-x+1)/log(2.0));
    if(L[dp[x][k]]>L[dp[y-(1<<k)+1][k]]) 
        return dp[y-(1<<k)+1][k];
    else return dp[x][k];
}
void solve() {
    int i,j,k,x,y,z,fxy,fxz,fyz;
    memset(vis,false,sizeof(vis)); 
    vis[0]=true; level=ief=0;
    dfs(0); init_rmq(); 
    scanf("%d",&M);
    if(g>1) printf("\n");
    printcase();
    for(i=0;i<M;i++) {
        scanf("%d%d%d",&x,&y,&z);
        fxy=E[query(H[x],H[y])]; fxz=E[query(H[x],H[z])];
        fyz=E[query(H[y],H[z])];
        if(fxz==z && fyz==z) {
            if(fxy==z) puts("Yes");
            else puts("No");
        }
        else {
            if(fxz==z || fyz==z) puts("Yes");
            else puts("No");
        }
    }
}

int main() {
//    int ca; scanf("%d",&ca);
    while(scanf("%d",&N)!=EOF) get_data(),solve();
    return 0;
}