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 <vector>
#include <queue>
using namespace std;

int n,ans,s,t,isCut[1010],child[1010],ok[1010],vs[1010];
int low[1010],num[1010],step,d[1010],e[1010];
vector <int> a[1010];

void visit(int x)
{
    low[x]=num[x]=++step;
    for (int i=0;i<int(a[x].size());i++)
    {
        int y=a[x][i];
        if (y==d[x]) continue;
        if (num[y]) low[x]=min(low[x],num[y]);
        else d[y]=x, visit(y), low[x]=min(low[x],low[y]);
    }
}

void bfs(int x,int cut,int d[])
{
    for (int i=1;i<=n;i++) d[i]=0;
    queue <int> q;
    q.push(x); d[x]=1; d[cut]=1;
    if (x==cut) return;
    while (!q.empty())
    {
        x=q.front(); q.pop();
        for (int i=0;i<int(a[x].size());i++)
        {
            int y=a[x][i];
            if (!d[y]) d[y]=1, q.push(y);
        }
    }           
}

int connected(int x,int y)
{
    vs[x]=1;
    if (x==y) return 1;
    for (int i=0;i<int(a[x].size());i++)
        if (!vs[a[x][i]] && connected(a[x][i],y))
            return 1;
    return 0;
}

int main()
{
    int m,x,y;
    cin >> n >> m >> s >> t;
    while (m--) cin >> x >> y, a[x].push_back(y), a[y].push_back(x);

    if (!connected(s,t))
    {
        cout << 0 << endl;
        return 0;
    }

    for (int i=1;i<=n;i++) 
        if (!d[i]) visit(i);
    for (int i=1;i<=n;i++) child[d[i]]++;
    for (int i=1;i<=n;i++)
        if (d[i] && !isCut[d[i]])
            if (low[i]>=num[d[i]] && (d[d[i]] || child[d[i]]>1))
                isCut[d[i]]=1;
    for (int i=1;i<=n;i++) ok[i]=1;

    for (int i=1;i<=n;i++)
        if (isCut[i])
        {
            bfs(s,i,d);
            bfs(t,i,e);
            for (int j=1;j<=n;j++) ok[j]&=(d[j]|e[j]);          
        }

    for (int i=1;i<=n;i++) ans+=ok[i];
    cout << ans << endl;
    for (int i=1;i<=n;i++)
        if (ok[i]) cout << i << endl;
}

Code mẫu của ladpro98

#include <bits/stdc++.h>

using namespace std;

const int N = 1e3 + 3;

int tin[N], low[N];
bool was[N];

vector<int> a[N];
set<int> answer;

int n, m, s, t;

void visit(int u) {
    was[u] = true;
    for (int v : a[u]) if (!was[v]) visit(v);
}

bool sameComponent() {
    visit(s);
    return was[t];
}

stack<pair<int, int> > S;
int Time;

void dfs(int u, int p = 0) {
    tin[u] = ++Time; low[u] = N;
    for (int v : a[u]) if (v != p) {
        if (tin[v]) {
            low[u] = min(low[u], tin[v]);
        } else {
            S.push({u, v});
            dfs(v, u);
            low[u] = min(low[u], low[v]);
            if (low[v] >= tin[u]) {
                set<int> cur;
                while (S.top() != make_pair(u, v)) {
                    cur.insert(S.top().second);
                    S.pop();
                }
                cur.insert(u); cur.insert(v); S.pop();
                if (cur.count(s) && cur.count(t)) {
                    answer = cur;
                }
            }
        }
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin >> n >> m >> s >> t;
    bool hasEdge = false;
    for (int i = 1; i <= m; ++i) {
        int u, v; cin >> u >> v;
        a[u].push_back(v); a[v].push_back(u);
        hasEdge |= (u == s && v == t) || (u == t && v == s);
    }
    if (!sameComponent()) return cout << 0, 0;
    if (!hasEdge) a[s].push_back(t), a[t].push_back(s);
    for (int i = 1; i <= n; ++i) if (!tin[i]) dfs(i);
    cout << answer.size() << endl;
    for (int u : answer) cout << u << '\n';
    return 0;
}

Code mẫu của RR

//Wishing myself a happy lunar new year with a lot of accept solutions
//Written by Nguyen Thanh Trung
{$R+,Q+}
uses math;
const
  FINP='';
  FOUT='';
  MAXN=2002;
var
  f1,f2:text;
  n,s,t,count,first,last:longint;
  fl,a,c:array[0..MAXN,0..MAXN] of longint;
  deg,luu,ok,xet,queue,trace:array[0..MAXN] of longint;
  path:boolean;
procedure openF;
begin
  assign(f1,FINP); reset(f1);
  assign(f2,FOUT); rewrite(f2);
end;
procedure closeF;
begin
  close(f1); close(f2);
end;
procedure inp;
var
  m,u,v,i:longint;
begin
  path:=false;
  read(f1,n,m,s,t);
  for i:=1 to n do
    if (i<>s) and (i<>t) then
      begin
        deg[i]:=1;
        a[i,1]:=i+n;
        c[i,i+n]:=1;
      end
    else
      begin
        deg[i]:=1;
        a[i,1]:=0;
        c[i,0]:=1;
      end;
  for i:=1 to m do
    begin
      read(f1,u,v);
      if ((u=s) and (v=t)) or ((u=t) and (v=s)) then
        begin
          path:=true;
          continue;
        end;
      inc(deg[u+n]); a[u+n,deg[u+n]]:=v; c[u+n,v]:=2;
      inc(deg[v+n]); a[v+n,deg[v+n]]:=u; c[v+n,u]:=2;
    end;
end;
procedure ans;
var
  i:longint;
begin
  if count>0 then
    begin
      ok[s]:=1; ok[t]:=1;
      inc(count,2);
    end;
  if (count=0) and path then
    begin
      ok[s]:=1; ok[t]:=1;
      count:=2;
    end;
  writeln(f2,count);
  for i:=1 to n do
    if ok[i]=1 then writeln(f2,i);
end;
procedure init(u:longint);
begin
  fillchar(xet,sizeof(xet),0); xet[u]:=1;
  fillchar(trace,sizeof(trace),0);
  first:=1; last:=1; queue[1]:=u;
end;
procedure findPath;
var
  u,i,v:longint;
begin
  while first<=last do
    begin
      u:=queue[first]; inc(first);
      for i:=1 to deg[u] do
        begin
          v:=a[u,i];
          if (xet[v]=0) and (c[u,v]>fl[u,v]) then
            begin
              trace[v]:=u;
              xet[v]:=1; inc(last); queue[last]:=v;
            end
          else if (xet[v]=0) and (fl[v,u]>0) then
            begin
              trace[v]:=-u;
              xet[v]:=1; inc(last); queue[last]:=v;
            end;
          if xet[0]=1 then exit;
        end;
    end;
end;
procedure incFlow(start:longint);
var
  v,u:longint;
begin
  u:=0;
  while u<>start do
    begin
      v:=trace[u];
      fl[v,u]:=1;
      u:=v;
    end;
end;
procedure erase(start:longint);
var
  v,u:longint;
begin
  u:=0;
  while u<>start do
    begin
      v:=luu[u];
      fl[v,u]:=0;
      u:=v;
    end;
end;
procedure solve;
var
  i:longint;
begin
  count:=0;
  for i:=1 to n do
  if (i<>s) and (i<>t) then
    begin
      c[i,i+n]:=2;
      init(i); findPath;
      if xet[0]=0 then begin c[i,i+n]:=1; continue; end;
      incFlow(i); luu:=trace;
      init(i);
      findPath;
      if xet[0]=0 then begin c[i,i+n]:=1; erase(i); continue; end;
      erase(i);
      ok[i]:=1; inc(count);
      c[i,i+n]:=1;
    end;
end;
begin
  openF;
  inp;
  solve;
  ans;
  closeF;
end.