Lưu ý: Các code mẫu dưới đây chỉ mang tính tham khảo và có thể không AC được bài tập này

Code mẫu của flashmt

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <vector>
using namespace std;
const int N = 100100;

struct segmentTree
{
    int low, high, mid, black;
    segmentTree *L, *R;

    segmentTree() {}
    segmentTree(int _low, int _high)
    {
        low = _low; high = _high; mid = (low + high) / 2;
        black = -1;
        if (low < high)
        {
            L = new segmentTree(low, mid);
            R = new segmentTree(mid + 1, high);
        }
    }

    void update(int x, int v)
    {
        if (low == high) 
        {
            if (black < 0) black = v;
            else black = -1;
        }
        else
        {
            if (x <= mid) L -> update(x, v);
            else R -> update(x, v);
            if (L -> black < 0) black = R -> black;
            else black = L -> black;
        }
    }

    int get(int x, int y)
    {
        if (low == x && high == y) return black;
        int u = -1;
        if (x <= mid) u = L -> get(x, min(y, mid));
        if (u > 0) return u;
        if (mid < y) return R -> get(max(x, mid + 1), y);
        return -1;
    }
};

int n, par[N], s[N], heavyDown[N], heavyUp[N];
int sizeChain[N], idChain[N], posChain[N], numChain, firstOnChain[N];
vector <int> a[N];
vector <segmentTree> tree;

void visit(int x)
{
    s[x] = 1;
    for (int i = 0; i < int(a[x].size()); i++) 
    {
        int y = a[x][i];
        if (y != par[x]) 
        {
            par[y] = x; 
            visit(y); 
            s[x] += s[y];
        }
    }

    for (int i = 0; i < int(a[x].size()); i++) 
    {
        int y = a[x][i];
        if (y != par[x] && s[y] * 2 >= s[x]) heavyDown[x] = y, heavyUp[y] = 1;
    }
}

void initHeavyLight()
{
    visit(1);
    for (int i = 1; i <= n; i++)
    {
        int x = i;
        if (heavyUp[x]) continue;
        firstOnChain[numChain] = x;
        while (x)
        {
            idChain[x] = numChain;
            posChain[x] = sizeChain[numChain]++;
            x = heavyDown[x];
        }
        tree.push_back(segmentTree(0, sizeChain[numChain++] - 1));
    }
}

int main()
{
    int Q, x, y, type;
    cin >> n >> Q;
    for (int i = 1; i < n; i++)
    {
        scanf("%d%d", &x, &y);
        a[x].push_back(y);
        a[y].push_back(x);
    }

    initHeavyLight();
    while (Q--)
    {
        scanf("%d%d", &type, &x);
        if (type) 
        {
            int ans = -1;
            while (x)
            {
                int u = tree[idChain[x]].get(0, posChain[x]);
                if (u > 0) ans = u;
                x = par[firstOnChain[idChain[x]]];
            }
            printf("%d\n", ans);
        }
        else tree[idChain[x]].update(posChain[x], x);
    }
}

Code mẫu của ladpro98

//by ladpro98
//Heavy - Light Decomposition
#include <bits/stdc++.h>
#define SetLength(a, n, t) free(a), a=(t*) calloc(n, sizeof(t))

const int N = 100005;
const int oo = 2000000000;
const int C = N;
using namespace std;
int n, q;
vector<int> a[N];
int Size[N], par[N], chainHead[N], chainNo, chainPos[N], chainID[N], chainSize[N];

struct segment_tree {
    int n; int *tree; int *node;
    void init(int _n);
    void Upd(int k, int l, int r, int x);
    void Upd(int x) {Upd(1, 1, n, x);}
    int Get(int k, int l, int r, int i, int j);
    int Get(int i, int j) {return Get(1, 1, n, i, j);}
};

segment_tree t[C];

void segment_tree :: init(int _n) {
    n = _n;
    SetLength(tree, 4 * n, int);
    SetLength(node, n + 2, int);
    for(int i=1; i<=4 * n; i++) tree[i] = oo;
}

void segment_tree :: Upd(int k, int l, int r, int x) {
    if (l > r || r < x || x < l) return;
    if (l == r) {
        if (tree[k] == oo) tree[k] = l; else tree[k] = oo;
        return;
    }
    int mid = (l + r) >> 1;
    Upd(k + k, l, mid, x);
    Upd(k + k + 1, mid + 1, r, x);
    tree[k] = min(tree[k + k], tree[k + k + 1]);
}

int segment_tree :: Get(int k, int l, int r, int i, int j) {
    if (l > r || r < i || j < l) return oo;
    if (i <= l && r <= j) return tree[k];
    int mid = (l + r) >> 1;
    return min(Get(k+k, l, mid, i, j), Get(k+k+1, mid + 1, r, i, j));
}

void Enter() {
    scanf("%d %d", &n, &q);
    int i, u, v;
    for(i=1; i<n; i++) {
        scanf("%d %d", &u, &v);
        a[u].push_back(v); a[v].push_back(u);
    }
}

void DFS(int u) {
    int i, v; Size[u] = 1;
    for(i=0; i<a[u].size(); i++) {
        v = a[u][i];
        if (v != par[u]) {
            par[v] = u;
            DFS(v);
            Size[u] += Size[v];
        }
    }
}

void HLD(int u) {
    if (chainHead[chainNo] == -1) chainHead[chainNo] = u;
    chainID[u] = chainNo;
    chainPos[u] = ++chainSize[chainNo];
    int ind = -1, ma = -1;
    for(int i=0; i<a[u].size(); i++)
    if (a[u][i] != par[u])
    if (ma < Size[a[u][i]]) {
        ma = Size[a[u][i]];
        ind = i;
    }
    if (ind >=0 ) HLD(a[u][ind]);
    for(int i=0; i<a[u].size(); i++)
    if (a[u][i] != par[u]) {
        if (i != ind) {
            chainNo++;
            HLD(a[u][i]);
        }
    }
}

void init_Helper() {
    for(int i=1; i<C; i++) chainHead[i] = -1;
    chainNo = 1;
    DFS(1);
    HLD(1);
    for(int i=1; i<=chainNo; i++) t[i].init(chainSize[i]);
    for(int i=1; i<=n; i++) t[chainID[i]].node[chainPos[i]] = i;
}

int query(int u, int v) {
    int res = oo, pos = oo;
    while (1) {
        if (chainID[u] == chainID[v]) {
            pos = t[chainID[u]].Get(1, chainPos[u]);
            if (pos < oo)
                res = t[chainID[u]].node[pos];
            break;
        }
        pos = t[chainID[u]].Get(1, chainPos[u]);
        if (pos < oo)
            res = t[chainID[u]].node[pos];
        u = par[chainHead[chainID[u]]];
    }
    return res;
}

int main()
{
    Enter();
    init_Helper();
    int kind, u, r;
    while (q--) {
        scanf("%d %d", &kind, &u);
        if (kind == 0)
            t[chainID[u]].Upd(chainPos[u]);
        else {
            r = query(u, 1);
            if (r < oo) printf("%d\n", r);
            else printf("-1\n");
        }
    }
    return 0;
}

Code mẫu của RR

//Written by Nguyen Thanh Trung
{$R+,Q+}
uses math;
const
  FINP='';
  FOUT='';
  MAXN=100001;
type
  list=^node;
  node=record
         u:longint;
         next:list;
       end;
var
  f1,f2:text;
  n,q,count:longint;
  ke:array[1..MAXN] of list;
  num,sc,color:array[1..MAXN] of longint;
  trace,d,head,size:array[1..MAXN] of longint;
  first:array[1..MAXN] of array of longint;
procedure openF; inline;
begin
  assign(f1,FINP); reset(f1);
  assign(f2,FOUT); rewrite(f2);
end;
procedure closeF; inline;
begin
  close(f1); close(f2);
end;
procedure add(u:longint; var a:list); inline;
var
  p:list;
begin
  new(p); p^.u:=u;
  p^.next:=a; a:=p;
end;
function cal(n:longint):longint; inline;
var
  temp:longint;
begin
  temp:=trunc(ln(n)/ln(2)+2);
  cal:=1<<temp+2;
end;
procedure inp; inline;
var
  i,u,v:longint;
begin
  read(f1,n,q);
  for i:=1 to n-1 do
    begin
      read(f1,u,v);
      add(u,ke[v]);
      add(v,ke[u]);
    end;
end;
procedure dfs1(u:longint); inline;
var
  v:longint;
  p:list;
begin
  sc[u]:=1;
  p:=ke[u];
  while p<>nil do
    begin
      v:=p^.u; p:=p^.next;
      if sc[v]>0 then continue;
      dfs1(v);
      inc(sc[u],sc[v]);
    end;
end;
procedure dfs2(u:longint); inline;
var
  v,next,ln:longint;
  p:list;
begin
  inc(count); num[u]:=count;
  ln:=-1; next:=0;
  p:=ke[u];
  while p<>nil do
    begin
      v:=p^.u; p:=p^.next;
      if head[v]>0 then continue;
      if sc[v]>ln then
        begin ln:=sc[v]; next:=v; end;
    end;
  if next=0 then exit;
  head[next]:=head[u]; d[next]:=d[u]+1; inc(size[head[u]]);
  dfs2(next);
  p:=ke[u];
  while p<>nil do
    begin
      v:=p^.u; p:=p^.next;
      if head[v]>0 then continue;
      trace[v]:=u; head[v]:=v; size[v]:=1; d[v]:=1;
      dfs2(v);
    end;
end;
procedure solve; inline;
var
  i:longint;
begin
  count:=0; head[1]:=1; d[1]:=1; size[1]:=1;
  dfs1(1);
  dfs2(1);
  for i:=1 to n do
    if head[i]=i then
      setlength(first[i],cal(size[i]));
end;
procedure update(tree,u,k:longint);
  procedure visit(i,l,r:longint); inline;
  var
    mid:longint;
  begin
    if l>r then exit;
    if (d[u]<l) or (r<d[u]) then exit;
    if (l=r) then
      begin
        if k=0 then first[tree,i]:=0
        else first[tree,i]:=u;
        exit;
      end;
    mid:=(l+r)>>1;
    visit(i<<1,l,mid);
    visit(i<<1+1,mid+1,r);
    if first[tree,i<<1]>0 then first[tree,i]:=first[tree,i<<1]
    else first[tree,i]:=first[tree,i<<1+1];
  end;
begin
  visit(1,1,size[tree]);
end;
function get(tree,u:longint):longint; inline;
var
  kq:longint;
  procedure visit(i,l,r:longint); inline;
  var
    mid:longint;
  begin
    if l>r then exit;
    if u<l then exit;
    if u>=r then
      begin
        if first[tree,i]>0 then kq:=first[tree,i];
        exit;
      end;
    mid:=(l+r)>>1;
    visit(i<<1,l,mid);
    if kq=0 then visit(i<<1+1,mid+1,r);
  end;
begin
  kq:=0;
  visit(1,1,size[tree]);
  get:=kq;
end;
function query(u:longint):longint; inline;
var
  h,x,kq:longint;
begin
  h:=head[u];
  if h>1 then
    begin
      kq:=query(trace[h]);
      if kq=0 then kq:=get(h,d[u]);
    end
  else kq:=get(h,d[u]);
  query:=kq;
end;
procedure ans;
var
  i,yc,u,kq:longint;
begin
  for i:=1 to q do
    begin
      read(f1,yc,u);
      if yc=0 then
        begin
          color[u]:=1-color[u];
          update(head[u],u,color[u]);
        end
      else
        begin
          kq:=query(u);
          if kq=0 then kq:=-1;
          writeln(f2,kq);
        end;
    end;
end;
begin
  openF;
  inp;
  solve;
  ans;
  closeF;
end.

Code mẫu của ll931110

//This program using heavy-light decomposition method, which is known with the name Dynamic Tree

{$MODE DELPHI,R+,Q+}
program QTREE3;
const
  input  = '';
  output = '';
  maxn = 100000;
type
  pnode = ^tnode;
  tnode = record
    val: integer;
    link: pnode;
  end;
var
  fi,fo: text;
  n,q,dyna: integer; //dyna: number of node in dynamic tree
  tree: array[1..4 * maxn] of integer;
  stat: array[1..maxn] of boolean;
  a: array[1..maxn] of pnode;
  lab,pos,size,maxnode: array[1..maxn] of integer;
  pr,st,fin: array[1..maxn] of integer;
  u1,u2,k: integer;  //Use for queries in Interval Tree
  ch: boolean;
  tk,res: integer;

procedure openfile;
begin
  assign(fi, input);
    reset(fi);

  assign(fo, output);
    rewrite(fo);
end;

procedure add(u,v: integer);
var
  p: pnode;
begin
  new(p);
  p^.val := v;
  p^.link := a[u];
  a[u] := p;
end;

procedure init;
var
  i,u,v: integer;
begin
  readln(fi, n, q);
  for i := 1 to n do a[i] := nil;
  for i := 1 to n - 1 do
    begin
      readln(fi, u, v);
      add(u,v);
      add(v,u);
    end;
end;

procedure prepare;
begin
  fillchar(pr, sizeof(pr), 0);
  fillchar(pos, sizeof(pos), 0);
end;



//Dynamic tree construction

procedure DFS(u: integer);
var
  p: pnode;
  max,v: integer;
begin
  p := a[u];
  size[u] := 1;
  max := 0;

  while p <> nil do
    begin
      v := p^.val;
      if v <> pr[u] then
        begin
          pr[v] := u;
          DFS(v);

          size[u] := size[u] + size[v];
          if size[v] > max then
            begin
              max := size[v];
              maxnode[u] := v;
            end;
        end;
      p := p^.link;
    end;
end;

procedure struct(u: integer);
var
  p: pnode;
  v,endnode: integer;
begin
  p := a[u];
  if (pos[u] = 0) and (p <> nil) then
    begin
      inc(dyna);
      pos[u] := dyna;
      lab[dyna] := u;
      st[u] := u;
      endnode := u;

      v := maxnode[u];
      while v <> 0 do
        begin
          inc(dyna);
          pos[v] := dyna;
          lab[dyna] := v;
          st[v] := u;
          if maxnode[v] = 0 then endnode := v;
          v := maxnode[v];
        end;

      v := u;
      while v <> 0 do
        begin
          fin[v] := endnode;
          v := maxnode[v];
        end;
    end;

  while p <> nil do
    begin
      v := p^.val;
      if v <> pr[u] then struct(v);
      p := p^.link;
    end;
end;

//End of Dynamic tree construction



procedure upIT(i,low,high: integer);
var
  mid: integer;
begin
  if low = high then
    begin
      if ch then tree[i] := low else tree[i] := -1;
      exit;
    end;

  mid := (low + high) div 2;
  if k <= mid then upIT(2 * i,low,mid) else
                   upIT(2 * i + 1,mid + 1,high);

  if tree[2 * i] = -1 then tree[i] := tree[2 * i + 1] else tree[i] := tree[2 * i];
end;

procedure calc(i,low,high: integer);
var
  mid: integer;
begin
  if (u2 < low) or (high < u1) then exit;
  if (u1 <= low) and (high <= u2) then
    begin
      if (tree[i] <> -1) and ((tk = -1) or (tk > tree[i])) then tk := tree[i];
      exit;
    end;

  mid := (low + high) div 2;
  calc(2 * i,low,mid);
  calc(2 * i + 1,mid + 1,high);
end;

procedure update(y: integer);
begin
  k := pos[y];
  stat[y] := not stat[y];
  ch := stat[y];
  if pos[y] <> 0 then upIT(1,1,dyna);
end;

procedure ask(y: integer);
var
  tmp: integer;
begin
  if y = 0 then exit;
  if stat[y] then tmp := y else tmp := -1;
  if tmp <> -1 then res := tmp;

  if (y = st[y]) or (pos[y] = 0) then ask(pr[y])
  else
    begin
      u1 := pos[st[y]];
      u2 := pos[y];
      tk := -1;
      calc(1,1,dyna);
      if tk <> -1 then res := lab[tk];
      ask(pr[st[y]]);
    end;
end;

procedure query;
var
  i,x,y: integer;
begin
  DFS(1);
  dyna := 0;
  struct(1);

  for i := 1 to 4 * dyna do tree[i] := -1;
  fillchar(stat, sizeof(stat), false);

  for i := 1 to q do
    begin
      readln(fi, x, y);
      if x = 0 then update(y) else
        begin
          res := -1;
          ask(y);
          writeln(fo, res);
        end;
    end;
end;

procedure closefile;
begin
  close(fo);
  close(fi);
end;

begin
  openfile;
  init;
  prepare;
  query;
  closefile;
end.