??????????????

??

????????????a?b????????????c??????????????????????????????????????????????

??????b???a??????????????a??????????[depth[a]+1, depth[a]+k]????????se[i]-1??????k?

??????a???b??????????????b??????????[depth[b]+1, depth[b]+k]????????se[i]-1??????k?

??

????????????????????????????????????????????????Heavy-Light Decomposition, HLD???????????????????????????????DFS?????????????????????????????????????????????????

???????

????????????????????????????????

???????????????????????????????

???????

??????????????????????????????

??????????????DFS????????????????

?????????????????????????????

?????????

???????DFS??????????

??????????????????????

?????????

???????????????????????????O(log n)?

??

????????

root   /   \  a     b

?????????[2, 3]???k=2?
- ?????[depth[a]+1, depth[a]+k] = [2, 4]
- ?????depth[a]?depth[b]??2?3?

????

#include 
   
    #include 
    
     #include 
     
      #include 
      #include 
       
        #include 
        
         #include 
         
          #include 
          
           #include 
           
            #include 
            
             #include 
             
              #include 
              
               using namespace std;typedef long long LL;typedef unsigned long long ULL;typedef pair
               
                 PII;const int N = 1000010;const int mod = 1e9 + 7;const double eps = 1e-6;int root[N], dfn[N], se[N], depth[N];vector
                
                  v[N];int idx = 1;struct Node { int l, r; LL sum;};void dfs1(int u, int fa) { se[u] = 1; dfn[u] = ++idx; depth[u] = depth[fa] + 1; for (int x : v[u]) { if (x != fa) { dfs1(x, u); se[u] += se[x]; } }}void dfs2(int u, int fa) { insert(root[dfn[u] - 1], root[dfn[u]], 1, N, depth[u], se[u] - 1); for (int x : v[u]) { if (x != fa) { dfs2(x, u); } }}void insert(int p, int &q, int l, int r, int pos, int x) { q = ++idx; tr[q] = tr[p]; tr[q].sum += x; if (l == r) return; int mid = (l + r) >> 1; if (pos <= mid) { insert(tr[p].l, tr[q].l, l, mid, pos, x); } else { insert(tr[p].r, tr[q].r, mid + 1, r, pos, x); }}LL query(int p, int q, int l, int r, int ql, int qr) { if (l > ql && r <= qr) return tr[q].sum - tr[p].sum; LL ans = 0; int mid = (l + r) >> 1; if (ql <= mid) ans += query(tr[p].l, tr[q].l, l, mid, ql, qr); if (qr > mid) ans += query(tr[p].r, tr[q].r, mid + 1, r, ql, qr); return ans;}void main() { cin.sync_with_stdio(false); cin.tie(0); int n, m; for (int i = 1; i < n; ++i) { int a, b; cin >> a >> b; v[a].push_back(b); v[b].push_back(a); } dfs1(1, 0); dfs2(1, 0); while (m--) { int p, k; cin >> p >> k; LL ans = min(depth[p] - 1, k) * (se[p] - 1); ans += query(root[dfn[p]], root[dfn[p] + se[p] - 1], 1, N, depth[p] + 1, min(depth[p] + k, N)); cout << ans << endl; } return 0;}