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>
using namespace std;

int n,q,a[100100],p[100100],d[100100];

int main()
{
    cin >> n >> q;
    for (int i=1;i<=n;i++) scanf("%d",p+i);

    for (int i=1;i<=n;i++)
    {
        int j=i;
        while (!d[j]) d[j]=i, j=p[j];
    }

    for (int i=2;i<=n;i++)
        if (d[i]==d[1]) d[i]=d[2];
    d[1]=d[2];

    int x,y;
    while (q--)
    {
        scanf("%d%d",&x,&y);
        puts(d[x]==d[y]?"Yes":"No");
    }
}

Code mẫu của ladpro98

#include <bits/stdc++.h>

using namespace std;

const int N = 100005;

int p[N];
int cycle[N];
int n, m, nCycle;

int main() {
    ios::sync_with_stdio(0); cin.tie(0);
    cin >> n >> m;
    for (int i = 1; i <= n; ++i) cin >> p[i];
    for (int i = 1; i <= n; ++i) if (!cycle[i]) {
        ++nCycle;
        for (int j = i; !cycle[j]; j = p[j])
            cycle[j] = nCycle;
    }
    int u, v;
    while (m--) {
        cin >> u >> v;
        bool YES = cycle[u] == cycle[v];
        YES |= cycle[u] == cycle[1] && cycle[v] == cycle[2];
        YES |= cycle[u] == cycle[2] && cycle[v] == cycle[1];
        cout << (YES ? "Yes\n" : "No\n");
    }
    return 0;
}

Code mẫu của RR

#include <sstream>
#include <iomanip>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <string>
#include <deque>
#include <complex>

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define FORN(i,a,b) for(int i=(a),_b=(b);i<_b;i++)
#define DOWN(i,a,b) for(int i=a,_b=(b);i>=_b;i--)
#define SET(a,v) memset(a,v,sizeof(a))
#define sqr(x) ((x)*(x))
#define ll long long
#define F first
#define S second
#define PB push_back
#define MP make_pair

#define DEBUG(x) cout << #x << " = "; cout << x << endl;
#define PR(a,n) cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl;
#define PR0(a,n) cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl;
using namespace std;

//Buffer reading
int INP,AM,REACHEOF;
#define BUFSIZE (1<<12)
char BUF[BUFSIZE+1], *inp=BUF;
#define GETCHAR(INP) { \
    if(!*inp) { \
        if (REACHEOF) return 0;\
        memset(BUF,0,sizeof BUF);\
        int inpzzz = fread(BUF,1,BUFSIZE,stdin);\
        if (inpzzz != BUFSIZE) REACHEOF = true;\
        inp=BUF; \
    } \
    INP=*inp++; \
}
#define DIG(a) (((a)>='0')&&((a)<='9'))
#define GN(j) { \
    AM=0;\
    GETCHAR(INP); while(!DIG(INP) && INP!='-') GETCHAR(INP);\
    if (INP=='-') {AM=1;GETCHAR(INP);} \
    j=INP-'0'; GETCHAR(INP); \
    while(DIG(INP)){j=10*j+(INP-'0');GETCHAR(INP);} \
    if (AM) j=-j;\
}
//End of buffer reading

const long double PI = acos((long double) -1.0);

int n, m, lab[100111];

int getRoot(int u) {
    if (lab[u] < 0) return u;
    return lab[u] = getRoot(lab[u]);
}

void merge(int u, int v) {
    u = getRoot(u);
    v = getRoot(v);
    if (u == v) return ;
    if (lab[u] < lab[v]) {
        lab[u] += lab[v];
        lab[v] = u;
    }
    else {
        lab[v] += lab[u];
        lab[u] = v;
    }
}

int main() {
    GN(n); GN(m);
    FOR(i,1,n) lab[i] = -1;
    int to;
    FOR(i,1,n) {
        GN(to);
        merge(i, to);
    }
    merge(1, 2);

    while (m--) {
        int u, v; GN(u); GN(v);
        if (getRoot(u) == getRoot(v)) puts("Yes");
        else puts("No");
    }
    return 0;
}

Code mẫu của hieult

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

using namespace std;

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

#define Rep(i,n) for(__typeof(n) i = 0; i < (n); ++i)
#define Repd(i,n) for(__typeof(n) i = (n)-1; i >= 0; --i)
#define For(i,a,b) for(__typeof(b) i = (a); i <= (b); ++i)
#define Ford(i,a,b) for(__typeof(a) 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))
#define nl puts("")
#define sp printf(" ")
#define ok puts("ok")
//#include <conio.h>

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> void db(T a, int p = -1) { if (p >= 0) cout << fixed << setprecision(p); cout << a << " "; }
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> struct Triple { T x, y, z; Triple() {} Triple(T _x, T _y, T _z) : x(_x), y(_y), z(_z) {} };
template<class T> Triple<T> euclid(T a, T b) { if (b == 0) return Triple<T>(1, 0, a); Triple<T> r = euclid(b, a % b); return Triple<T>(r.y, r.x - a / b * r.y, r.z); }
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 = 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;
}

const double PI = 2 * acos(0);
const string months[] = {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
const int days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
const int dr[] = {0, 0, -1, +1};
const int dc[] = {-1, +1, 0, 0};
const int inf = (int)1e9 + 5;
const ll linf = (ll)1e16 + 5;
const double eps = ld(1e-9);
const ll mod = 100000007;
typedef pair<int, int> II;


#define maxn 200005
#define maxv 1005

int n, m, a[maxn], dad[maxn], u, v;

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

    scanf("%d %d", &n, &m);
    ms(dad, 0);
    For(i, 1, n) scanf("%d", &a[i]);
    For(i, 1, n) if(!dad[i]){
        u = i;
        dad[u] = (i == 2 ? 1 : i);
        u = a[u];
        while(u != i){
            dad[u] = (i == 2 ? 1 : i);
            u = a[u];
        }
    }
    Rep(run, m){
        scanf("%d %d", &u, &v);
        if(dad[u] == dad[v]){
            printf("Yes\n");
        }
        else printf("No\n");
    }

    return 0;
}

Code mẫu của skyvn97

#include<stack>
#include<cstdio>
#include<cstring>
#define MAX   100100
using namespace std;
struct vector {
    int d[3];
    int sz;
    vector(){}
    void clear(void) {
        sz=0;
    }
    int size(void) const {
        return (sz);    
    }
    int operator [] (const int &i) const {
        return d[i];
    }
    void push_back(const int &val) {
        sz++;
        d[sz-1]=val;
    }
};
vector g[MAX];
int n,q,nc,cnt;
int p[MAX];
int ncp[MAX];
int low[MAX];
int num[MAX];
bool fr[MAX];
stack<int> st;
void init(void) {
    scanf("%d",&n);
    scanf("%d",&q);
    int i;
    for (i=1;i<=n;i=i+1) {
        scanf("%d",&p[i]);
        g[i].clear();
    }
    for (i=1;i<=n;i=i+1) {
        if (i==1 && p[i]==2) continue;
        if (i==2 && p[i]==1) continue;
        if (i==p[i]) continue;
        g[i].push_back(p[i]);
    }
    g[1].push_back(2);
    g[2].push_back(1);  
}
int min(const int &x,const int &y) {
    if (x<y) return (x); else return (y);
}
void visit(const int &u) {
    int i,v;
    cnt++;
    num[u]=cnt;
    low[u]=cnt;
    st.push(u);
    for (i=0;i<g[u].size();i=i+1) {
        v=g[u][i];
        if (fr[v]) {
            if (num[v]>0) low[u]=min(low[u],num[v]);
            else {
                visit(v);
                low[u]=min(low[u],low[v]);
            }
        }
    }
    if (low[u]==num[u]) {
        nc++;
        do {
            v=st.top();st.pop();
            fr[v]=false;
            ncp[v]=nc;
        }
        while (v!=u);
    }
}
void tarjan(void) {
    memset(low,0,sizeof low);
    memset(num,0,sizeof num);
    memset(fr,true,sizeof fr);
    cnt=0;nc=0;
    int i;
    for (i=1;i<=n;i=i+1)
        if (num[i]==0) visit(i);
}
void answer(void) {
    int i,u,v;
    for (i=1;i<=q;i=i+1) {
        scanf("%d",&u);
        scanf("%d",&v);
        if (ncp[u]==ncp[v]) printf("Yes\n");
        else printf("No\n");
    }
}
int main(void) {
    init();
    tarjan();
    answer();
    return 0;
}