点分治

非容斥方法

struct Edge {
    int to, net;
}edge[maxn * 2];
int head[maxn], cnt;

int n, k;
int dis[maxn], arr[maxn], sz[maxn], msz[maxn], tail, all, rt;
bool vis[maxn];

void init() {
    for(int i = 0; i <= n; i++) {
        head[i] = -1;
        vis[i] = 0;
    }
    cnt = 0;
}
void addedge(int u, int v) {
    edge[cnt] = (Edge){v, head[u]};
    head[u] = cnt++;
}
void Findrt(int pos, int pre) {
    sz[pos] = 1;
    msz[pos] = 0;
    for(int i = head[pos]; i != -1; i = edge[i].net) {
        int to = edge[i].to;
        if(to == pre || vis[to]) continue;
        Findrt(to, pos);
        sz[pos] += sz[to];
        msz[pos] = max(msz[pos], sz[to]);
    }
    msz[pos] = max(msz[pos], all - sz[pos]);
    if(msz[pos] < msz[rt] || rt == 0) rt = pos;
}
void dfs(int pos, int pre, int v) {
    arr[++tail] = v; //先保存下来
    for(int i = head[pos]; i != -1; i = edge[i].net) {
        int to = edge[i].to;
        if(vis[to] || to == pre) continue;
        dfs(to, pos, v);
    }
}
void query(int x) {
    
}
void add(int x) {

}
void divide(int pos) {
    vis[pos] = 1;
    for(int i = head[pos]; i != -1; i = edge[i].net) {
        int to = edge[i].to;
        if(vis[to]) continue;
        tail = 0;
        dfs(to, pos, v);
        for(int j = 1; j <= tail; j++) //先算对答案贡献
            query(j);
        for(int j = 1; j <= tail; j++) //再加入值
            add(j)
    }
    //清空影响
    for(int i = head[pos]; i != -1; i = edge[i].net) {
        int to = edge[i].to;
        if(vis[to]) continue;
        tail = 0;
        dfs(to, pos, 0);
    }
    //到下一层
    for(int i = head[pos]; i != -1; i = edge[i].net) {
        int to = edge[i].to;
        if(vis[to]) continue;
        all = sz[to]; 
        rt = 0;
        Findrt(to, 0);
        divide(rt);
    }
}

int main() {
    cin >> n;
    init();
    for(int i = 1; i < n; i++) {
        int u, v;
        cin >> u >> v;
        addedge(u, v);
        addedge(v, u);
    }
    all = n;
    rt = 0;
    Findrt(1, 0);
    divide(rt);
    //接下来输出
    return 0;
}