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

const fi='';
      fo='';
      maxn=110;
var n,m,last,sm,dem,re:longint;
    a,e:array[1..maxn,1..maxn] of boolean;
    b:array[1..maxn,1..maxn] of longint;
    free:array[1..maxn] of boolean;
    d,sl,low,num,st,dau,q:array[1..maxn] of longint;

procedure rf;
var i,x,y:longint;
begin
     assign(input,fi); reset(input);
     readln(n);
     readln(m);
     for i:=1 to m do
     begin
          readln(x,y);
          a[x,y]:=true;
          a[y,x]:=true;
     end;
     close(input);
end;

function pop:longint;
begin
     pop:=st[last];
     dec(last);
end;

procedure push(i:longint);
begin
     inc(last);
     st[last]:=i;
end;

function min(x,y:longint):longint;
begin
     if x<y then min:=x else min:=y;
end;

procedure visit(x,y:longint);
var i:longint;
begin
     inc(dem); num[x]:=dem; low[x]:=dem;
     push(x);
     for i:=1 to n do
         if free[i] and a[x,i] and (i<>y) then
         begin
              if num[i]>0 then low[x]:=min(num[i],low[x])
              else
              begin
                   visit(i,x);
                   low[x]:=min(low[x],low[i]);
              end;
         end;
     if num[x]=low[x] then
     begin
          inc(sm);
          repeat
                i:=pop;
                free[i]:=false;
                d[i]:=sm;
          until i=x;
          d[x]:=sm;
     end;
end;

procedure pr;
var i,j,k,l,high:longint;
begin
     last:=0; sm:=0; dem:=0;
     for i:=1 to n do free[i]:=true;
     for i:=1 to n do
         if free[i] then visit(i,0);
     for i:=1 to n do
     begin
          inc(sl[d[i]]);
          b[d[i],sl[d[i]]]:=i;
     end;
     re:=0;
     for i:=1 to n-1 do
         for j:=i+1 to n do
             if a[i,j] then
             begin
                  e[d[i],d[j]]:=true;
                  e[d[j],d[i]]:=true;
             end;
     for i:=1 to n-1 do
         for j:=i+1 to n do
         begin
              fillchar(dau,sizeof(dau),0);
              dau[d[i]]:=1; high:=1; q[1]:=d[i]; l:=1;
              repeat
                    for k:=1 to sm do
                        if (dau[k]=0) and e[q[l],k] then
                        begin
                             inc(high);
                             q[high]:=k;
                             dau[k]:=dau[q[l]]+1;
                        end;
                    inc(l);
              until (l>high) or (dau[d[j]]>0);
              if dau[d[j]]>0 then re:=re+dau[d[j]]-1;
         end;
end;

procedure wf;
begin
     assign(output,fo); rewrite(output);
     writeln(re);
     close(output);
end;

begin
     rf;
     pr;
     wf;
end.

Code mẫu của happyboy99x

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <functional>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;

typedef pair<int, int> ii;
typedef vector<ii> vii;
typedef vector<vii> vvii;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef long long LL;

#define sz(a) (int((a).size()))
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define all(c) (c).begin(), (c).end()
#define tr(c,i) for(typeof((c).begin()) i = (c).begin(), _e = (c).end(); i != _e; ++i)
#define present(c,x) ((c).find(x) != (c).end())
#define cpresent(c,x) (find(all(c),x) != (c).end())
#define rep(i,n) for(int i = 0, _n = (n); i < _n; ++i)
#define repd(i,n) for(int i = (n)-1; i >= 0; --i )
#define fo(i,a,b) for(int i = (a), _b = (b); i <= _b; ++i)
#define fod(i,a,b) for(int i = (a), _b = (b); i >= _b; --i)

#define INF 1000000000
#define N 105

int n, m;
vvi g; vii e;
int qu[N], lq, hq;
bool vst[N];

int bfs(int U, int V) {
    lq = 0; hq = 1; qu[0] = 0; memset(vst, 0, sizeof vst); vst[0] = 1;
    int res = 0;
    while(lq != hq) {
        int u = qu[lq++]; ++res;
        tr(g[u], it) {
            if(!vst[*it] && !(u == U && V == *it || U == *it && V == u)) {
                vst[*it] = 1;
                qu[hq++] = *it;
            }
        }
    }
    return res;
}

int main() {
#ifndef ONLINE_JUDGE
    freopen( "input.txt", "r", stdin );
    //freopen( "output.txt", "w", stdout );
#endif
    scanf("%d%d",&n,&m); g.resize(n);
    rep(i,m) {
        int u, v; scanf("%d%d",&u,&v);
        g[--u].pb(--v); g[v].pb(u);
        e.pb(ii(u,v));
    }
    LL res = 0;
    tr(e, it) {
        LL t = (LL) bfs(it->fi, it->se);
        res += t * (n-t);
    }
    printf("%lld\n", res);
    return 0;
}

Code mẫu của ladpro98

#include <bits/stdc++.h>

using namespace std;

const int N = 1000;

int par[N];
int size[N];
vector<int> a[N];

int low[N], num[N];

int n, m;
int Time;

void dfs(int u) {
    num[u] = ++Time; low[u] = N;
    size[u] = 1;
    for (int v : a[u]) if (v != par[u]) {
        if (num[v] == 0) {
            par[v] = u;
            dfs(v);
            low[u] = min(low[u], low[v]);
            size[u] += size[v];
        } else {
            low[u] = min(low[u], num[v]);
        }
    }
}

int main() {
    cin >> n >> m;
    for (int i = 1; i <= m; ++i) {
        int u, v; cin >> u >> v;
        a[u].push_back(v); a[v].push_back(u);
    }
    dfs(1);
    int ans = 0;
    for (int v = 2; v <= n; ++v) {
        if (low[v] >= num[v])
            ans += size[v] * (n - size[v]);
    }
    cout << ans << endl;
    return 0;
}

Code mẫu của RR

#include <iostream>
#include <algorithm>
#include <vector>

#define FOR(i,a,b)  for(int i=a; i<=b; i++)
#define FORD(i,a,b) for(int i=a; i>=b; i--)
#define FORV(i,v)   for(typeof(v.begin()) i=v.begin(); i!=v.end(); i++)
#define V vector<int>
#define _ [111]
using namespace std;

int n,m,res=0,now=0;
int low _, num _, father _, weight _;
V ke _;

void inp() {
    scanf("%d %d",&n,&m);
    FOR(i,1,m) {
        int u,v;
        scanf("%d %d",&u,&v);
        ke[u].push_back(v);
        ke[v].push_back(u);
    }
}

void dfs(int u) {
    now++; num[u]=now; low[u]=now;
    weight[u]=1;
    FORV(v,ke[u]) {
        if (*v==father[u]) continue;
        if (!father[*v]) {
            father[*v]=u;
            dfs(*v);
            weight[u]+=weight[*v];
            low[u]=min(low[u],low[*v]);
        }
        else low[u]=min(low[u],num[*v]);
    }
}

void solve() {
    father[1]=1; dfs(1);

    FOR(v,2,n) {
        int u=father[v];
        if (low[v]>num[u]) {
//            cout<<u<<" "<<v<<" "<<weight[v]<<endl;
            res+=weight[v]*(n-weight[v]);
        }
    }
    cout<<res;
}

int main() {
//    freopen("input.txt","r",stdin);
//    freopen("output.txt","w",stdout);
    inp();
    solve();
    return 0;
}

Code mẫu của hieult

#include <set>
#include <map>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iomanip>
#include <iostream>
#include <algorithm>
#include <ctime>
#include <deque>
#include <bitset>
#include <cctype>
#include <utility>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned int ui;
typedef unsigned long long ull;

#define Rep(i,n) for(int i = 0; i < (n); ++i)
#define Repd(i,n) for(int i = (n)-1; i >= 0; --i)
#define For(i,a,b) for(int i = (a); i <= (b); ++i)
#define Ford(i,a,b) for(int i = (a); i >= (b); --i)
#define Fit(i,v) for(__typeof((v).begin()) i = (v).begin(); i != (v).end(); ++i)
#define Fitd(i,v) for(__typeof((v).rbegin()) i = (v).rbegin(); i != (v).rend(); ++i)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(), (a).end()
#define ms(a,x) memset(a, x, sizeof(a))

template<class F, class T> T convert(F a, int p = -1) {
    stringstream ss;
    if (p >= 0)
        ss << fixed << setprecision(p);
    ss << a;
    T r;
    ss >> r;
    return r;
}
template<class T> T gcd(T a, T b) {
    T r;
    while (b != 0) {
        r = a % b;
        a = b;
        b = r;
    }
    return a;
}
template<class T> T lcm(T a, T b) {
    return a / gcd(a, b) * b;
}
template<class T> T sqr(T x) {
    return x * x;
}
template<class T> T cube(T x) {
    return x * x * x;
}
template<class T> int getbit(T s, int i) {
    return (s >> i) & 1;
}
template<class T> T onbit(T s, int i) {
    return s | (T(1) << i);
}
template<class T> T offbit(T s, int i) {
    return s & (~(T(1) << i));
}
template<class T> int cntbit(T s) {
    return s == 0 ? 0 : cntbit(s >> 1) + (s & 1);
}

const int bfsz = 1 << 16;
char bf[bfsz + 5];
int rsz = 0;
int ptr = 0;
char gc() {
    if (rsz <= 0) {
        ptr = 0;
        rsz = (int) fread(bf, 1, bfsz, stdin);
        if (rsz <= 0)
            return EOF;
    }
    --rsz;
    return bf[ptr++];
}
void ga(char &c) {
    c = EOF;
    while (!isalpha(c))
        c = gc();
}
int gs(char s[]) {
    int l = 0;
    char c = gc();
    while (isspace(c))
        c = gc();
    while (c != EOF && !isspace(c)) {
        s[l++] = c;
        c = gc();
    }
    s[l] = '\0';
    return l;
}
template<class T> bool gi(T &v) {
    v = 0;
    char c = gc();
    while (c != EOF && c != '-' && !isdigit(c))
        c = gc();
    if (c == EOF)
        return false;
    bool neg = c == '-';
    if (neg)
        c = gc();
    while (isdigit(c)) {
        v = v * 10 + c - '0';
        c = gc();
    }
    if (neg)
        v = -v;
    return true;
}

typedef pair<int, int> II;
const ld PI = acos(-1.0);
const ld eps = 1e-9;
const int dr[] = { -1, 0, +1, 0};
const int dc[] = { 0, +1, 0, -1};
const int inf = (int) 1e9 + 5;
const ll linf = (ll) 1e16 + 5;
const int mod = (ll) (1e9 + eps);
#define ok puts("ok")
#define maxn 105
#define maxe 20005

int last[maxn], adj[maxe], next[maxe], E = 0, flag[maxn], run, f[maxn], vt[maxn];
int n, m, res;

void add(int u, int v){
    adj[E] = v; next[E] = last[u]; last[u] = E++;
    adj[E] = u; next[E] = last[v]; last[v] = E++;
}

int cal(int par, int u){
    if(flag[u]) return 0;
    flag[u] = 1;
    int ret = 1;
    for(int e = last[u]; e != -1; e = next[e]){
        int v = adj[e];
        if(v == par) continue;
        ret += cal(u, v);
    }
    return ret;
}

void go(int par, int u){
    f[u] = run;
    vt[u] = run++;

    for(int e = last[u]; e != -1; e = next[e]){
        int v = adj[e];
        if(v == par) continue;
        if(vt[v] > -1) f[u] = min(f[u], vt[v]);
        else{
            go(u, v);
            f[u] = min(f[u], f[v]);
            if(f[v] > vt[u]){
                ms(flag, 0);
                int num = cal(u, v);
                res += num * (n - num);
            }
        }
    }

}

int main(){
//  freopen("in.txt", "r", stdin);

    cin >> n >> m;
    int u, v;
    ms(last, -1);
    Rep(mi, m){
        scanf("%d %d", &u, &v);
        add(u, v);
    }

    ms(f, -1); ms(vt, -1);
    res = 0;
    go(0, 1);
    run = 0;
    cout << res;

    return 0;
}

Code mẫu của ll931110

//#pragma comment(linker, "/STACK:16777216")
#include <algorithm>
#include <bitset>
#include <cmath>
#include <ctime>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <functional>
#include <iostream>
#include <map>
#include <set>
#include <sstream>
#include <stack>
#include <queue>
#include <vector>
#include <utility>
using namespace std;

int n,m;
vector<int> adj[105];
int low[105],num[105],sz[105],pre[105],cnt = 0;
long long ret = 0;

void DFS(int u)
{
    num[u] = low[u] = ++cnt;  sz[u] = 1;
    for (int i = 0; i < adj[u].size(); i++)
    {
        int v = adj[u][i];
        if (pre[u] == v) continue;
        if (!num[v])
        {
            pre[v] = u;  DFS(v);  sz[u] += sz[v];
            if (low[v] > num[u]) ret += 1LL * sz[v] * (n - sz[v]);
            low[u] = min(low[u],low[v]);
        }
        else if (pre[v] != u) low[u] = min(low[u],low[v]);
    }
}

int main()
{
//    freopen("weather.in","r",stdin);
//    freopen("weather.ou","w",stdout);
    scanf("%d %d", &n, &m);
    for (int i = 0; i < m; i++)
    {
        int x,y;  scanf("%d %d", &x, &y);
        if (x == y) continue;
        adj[x].push_back(y);
        adj[y].push_back(x);
    }
    memset(pre,-1,sizeof(pre));
    DFS(1);
    cout << ret << endl;
}

Code mẫu của skyvn97

#include<cstdio>
#include<vector>
#define MAXV   111
#define MAXE   5050
using namespace std;
struct edge {
    int u,v;    
};
vector<int> g[MAXV];
bool a[MAXV][MAXV];
edge e[MAXE];
int m,n,c,r;
int num[MAXV];
int low[MAXV];
int up[MAXV];
void loadgraph(void) {
    int i,j;
    scanf("%d",&n);
    scanf("%d",&m);
    for (i=1;i<=n;i=i+1)
        for (j=1;j<=n;j=j+1)
            a[i][j]=false;      
    for (i=1;i<=m;i=i+1) {
        scanf("%d",&e[i].u);
        scanf("%d",&e[i].v);
        g[e[i].u].push_back(e[i].v);
        g[e[i].v].push_back(e[i].u);
        a[e[i].u][e[i].v]=true;
        a[e[i].v][e[i].u]=true;
    }
    for (i=1;i<=n;i=i+1) num[i]=0;
    c=0;
}
int find(int x) {
    if (up[x]<0) return (x);
    up[x]=find(up[x]);
    return (up[x]);
}
void join(int a,int b) {
    int x=find(a);
    int y=find(b);
    if (x==y) return;
    up[x]=up[x]+up[y];
    up[y]=x;
}
int bridge(int u,int v) {
    int i;
    for (i=1;i<=n;i=i+1) up[i]=-1;
    for (i=1;i<=m;i=i+1) {
        if ((e[i].u==u) && (e[i].v==v)) continue;
        if ((e[i].u==v) && (e[i].v==u)) continue;
        join(e[i].u,e[i].v);
    }
    for (i=1;i<=n;i=i+1)
        if (up[i]<0) return ((-up[i])*(n+up[i]));
}
void visit(int u) {
    int i,v;
    c=c+1;
    num[u]=c;
    low[u]=n+1;
    for (i=0;i<g[u].size();i=i+1) {
        v=g[u][i];
        if (!a[u][v]) continue;     
        a[v][u]=false;
        if (num[v]==0) {
            visit(v);
            if (low[u]>low[v]) low[u]=low[v];
            if (low[v]>num[u]) r=r+bridge(u,v);
        }
        else 
            if (low[u]>num[v]) low[u]=num[v];
    }
}
void process(void) {
    int i;
    r=0;
    for (i=1;i<=n;i=i+1)
        if (num[i]==0) visit(i);
    printf("%d",r);
}
int main(void) {
    loadgraph();
    process();
    return 0;
}