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

int n, rank[100100], dist[100100], curRank;
pair <int,int> tr[100100];
vector <int> a[100100], c[100100];

int cmp(int u, int v)
{
    return make_pair(rank[tr[u].first], tr[u].second) < make_pair(rank[tr[v].first], tr[v].second);
}

int main()
{
    int m, x, y, z;
    cin >> n >> m;
    while (m--) 
    {
        scanf("%d%d%d", &x, &y, &z);
        a[x].push_back(y); c[x].push_back(z);
        a[y].push_back(x); c[y].push_back(z);
    }

    queue <int> q;
    vector <int> order;
    q.push(1); dist[1] = 1;
    while (1)
    {
        if (q.empty())
        {
            if (order.empty()) break;
            sort(order.begin(), order.end(), cmp);
            for (int i = 0; i < int(order.size()); i++)
            {
                int x = order[i];
                if (!i || cmp(order[i - 1], x)) curRank++;
                rank[x] = curRank;
                q.push(x);
            }
            order.clear();
        }

        x = q.front(); q.pop();
        for (int i = 0; i < int(a[x].size()); i++)
        {
            y = a[x][i]; z = c[x][i];
            if (!dist[y] || (dist[y] == dist[x] + 1 && make_pair(rank[x], z) < make_pair(rank[tr[y].first], tr[y].second)))
            {
                if (!dist[y]) order.push_back(y);
                dist[y] = dist[x] + 1;
                tr[y] = make_pair(x, z);
            }
        }
    }

    cout << dist[n] - 1 << endl;
    vector <int> pathColor;
    while (n != 1) pathColor.push_back(tr[n].second), n = tr[n].first;
    for (int i = int(pathColor.size()) - 1; i >= 0; i--) printf("%d ", pathColor[i]);
}

Code mẫu của happyboy99x

#include<algorithm>
#include<iostream>
#include<cassert>
#include<cstdio>
#include<limits>
#include<queue>
using namespace std;

#define TR(v,i) for(__typeof((v).begin())i=(v).begin();i!=(v).end();++i)
const int N = 1e5;
vector<pair<int, int> > g[N];
int n, m, d[N];

void enter() {
    cin >> n >> m;
    for(int i = 0; i < m; ++i) {
        int u, v, c;
        cin >> u >> v >> c;
        --u; --v;
        g[u].push_back(make_pair(v, c));
        g[v].push_back(make_pair(u, c));
    }
}

void bfs() {
    fill_n(d, n, -1); d[n - 1] = 0;
    queue<int> q; q.push(n - 1);
    while(!q.empty()) {
        int u = q.front(); q.pop();
        TR(g[u], it) {
            int v = it->first;
            if(d[v] != -1) continue;
            d[v] = d[u] + 1;
            q.push(v);
        }
    }
}

pair<int, int> trace[N];

void solve() {
    fill_n(trace, n, make_pair(-1, -1));
    queue<int> q; q.push(0);
    for(int step = 0; !q.empty(); ++step) {
        queue<int> nextQueue;
        int bestColor = numeric_limits<int>::max();
        while(!q.empty()) {
            int u = q.front(); q.pop();
            TR(g[u], it) {
                int v = it->first, c = it->second;
                if(d[u] - 1 != d[v])
                    continue;
                if(c < bestColor) {
                    while(!nextQueue.empty()) {
                        int u = nextQueue.front();
                        trace[u] = make_pair(-1, -1);
                        nextQueue.pop();
                    }
                    bestColor = c;
                }
                if(c == bestColor) {
                    if(trace[v].first != -1) continue;
                    nextQueue.push(v);
                    trace[v] = make_pair(u, c);
                }
            }
        }
        q = nextQueue;
    }
    vector<int> res;
    for(int u = n - 1; u != 0; u = trace[u].first)
        res.push_back(trace[u].second);
    reverse(res.begin(), res.end());
    assert((int) res.size() == d[0]);
    printf("%d\n", d[0]);
    for(int i = 0; i < (int) res.size(); ++i)
        printf("%d%c", res[i], i + 1 == (int) res.size() ? '\n' : ' ');
}

int main() {
    ios::sync_with_stdio(false);
    enter();
    bfs();
    solve();
    return 0;
}

Code mẫu của ladpro98

#include <bits/stdc++.h>
#define ii pair<int, int>
#define X first
#define Y second
const int N = 100005;
const int oo = 1000000009;
using namespace std;
vector<ii> a[N];
bool was[N], possible[N], pushed[N];
int c[N], T[N], len[3][N], d[N];
int Q[N + N], res[N], st[N + N], deg[N];
int m, n, k, l, r, top;

void BFS() {
    int i, u, v;
    while (l <= r) {
        u = Q[l++];
        for(i=0; i<deg[u]; i++) {
            v = a[u][i].X;
            if (was[v]) continue;
            if (d[u] + 1 + len[2][v] != len[2][1]) continue;
            if (c[v] <= a[u][i].Y) continue;
            st[++top] = v;
            T[v] = u; c[v] = a[u][i].Y;
            d[v] = d[u] + 1;
        }
    }
}

void BFS_Init(int source, int p) {
    int l = 1, r = 1, i, u, v;
    Q[1] = source; len[p][source] = 0;
    for(i=1; i<=n; i++) was[i] = false;
    was[source] = true;
    while (l <= r) {
        u = Q[l++];
        for(i=0; i<deg[u]; i++) {
            v = a[u][i].X;
            if (!was[v]) {
                Q[++r] = v;
                len[p][v] = len[p][u] + 1;
                was[v] = true;
            }
        }
    }
}

int main()
{
    //freopen("MECUNG.inp", "r", stdin);
    //freopen("MECUNG.out", "w", stdout);
    scanf("%d %d\n", &n, &m);
    int i, u, v, cc;
    for(i=1; i<=m; i++) {
        scanf("%d %d %d\n", &u, &v, &cc);
        a[u].push_back(ii(v, cc));
        a[v].push_back(ii(u, cc));
    }
    for(i=1; i<=n; i++) deg[i] = a[i].size();
    BFS_Init(n, 2);
    for(i=1; i<=n; i++) {c[i] = oo; was[i] = false;}
    l = 1; r = 1; Q[1] = 1; was[1] = true;
    int layer, minC;
    while (true) {
        BFS(); if (T[n] > 0) break;
        minC = oo;
        for(i=1; i<=top; i++) minC = min(minC, c[st[i]]);
        for(i=1; i<=top; i++) if (c[st[i]] == minC && !pushed[st[i]]) {
            Q[++r] = st[i]; pushed[st[i]] = true;
        }
        for(i=1; i<=top; i++) was[st[i]] = true;
        top = 0;
    }
    printf("%d\n", len[2][1]);
    v = n;
    while (v != 1) {
        res[++k] = v;
        v = T[v];
    }
    for(i=k; i>0; i--) printf("%d ", c[res[i]]);

    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);
const int MN = 100111;

vector< pair<int,int> > ke[MN];
int m, n;

queue< stack<int> > q;
int tr[MN], trc[MN], d[MN];

void init() {
    FOR(i,1,n) ke[i].clear();
}

int top, st[MN], id[MN], now;

bool cmp(int u, int v) {
    return trc[u] < trc[v];
}

vector<int> res;

void trace(int n) {
    if (n == 1) return ;

    trace(tr[n]);
    res.PB(trc[n]);
}

int main() {
    while (scanf("%d%d", &n, &m) == 2) {
        init();

        while (m--) {
            int u, v, c; scanf("%d%d%d", &u, &v, &c);
            ke[u].PB(MP(v,c));
            ke[v].PB(MP(u,c));
        }

        memset(tr, -1, sizeof tr);
        memset(d, -1, sizeof d);
        tr[1] = 1; d[1] = 0;

        now = 0;
        id[1] = ++now;

        stack<int> cur; cur.push(1);
        q.push(cur);

        while (!q.empty()) {
            cur = q.front(); q.pop();
            top = 0;
            // cout << "cur = ";
            while (!cur.empty()) {
                int u = cur.top(); cur.pop();
                // cout << u << ' ';
                REP(i,ke[u].size()) {
                    int v = ke[u][i].F;
                    if (tr[v] < 0) {
                        d[v] = d[u] + 1;
                        tr[v] = u;
                        trc[v] = ke[u][i].S;

                        st[++top] = v;
                    }
                    else if (id[tr[v]] == id[u] && trc[v] > ke[u][i].S) {
                        trc[v] = ke[u][i].S;
                        tr[v] = u;
                    }
                }
            }
            // cout << endl;

            sort(st+1, st+top+1, cmp);

            // PR(st, top);
            // FOR(i,1,top) cout << trc[st[i]] << ' '; cout << endl;

            int last = -1;
            FOR(i,1,top) {
                if (trc[st[i]] != last) {
                    stack<int> tmp;
                    q.push(tmp);
                    ++now;
                }
                q.back().push(st[i]);
                id[st[i]] = now;
                last = trc[st[i]];
            }

            // DEBUG(q.size());
        }

        res.clear();
        trace(n);

        printf("%d\n", res.size());
        REP(i,res.size()) printf("%d ", res[i]);
        puts("");

        break;
    }
    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>
#include <cassert>

using namespace std;

typedef long long ll;
typedef 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[] = {0, +1, 0, -1};
const int dc[] = {+1, 0, -1, 0};

const int inf = (int)1e9 + 5;
const ll linf = (ll)1e16 + 5;
const ll mod = (ll)1e9 + 7;

#define maxn 400005

struct triple{
    int id, x, y;
    triple(){};
    triple(int _id, int _x, int _y){
        id = _id; x = _x; y = _y;
    }
    bool operator <(const triple &T)const{
        if(x == T.x) return y < T.y;
        return x < T.x;
    }
}T[maxn];

int f[maxn], d[maxn], back[maxn], que[maxn], que1[maxn];
int adj[maxn], next[maxn], last[maxn], color[maxn], Color[maxn], E;
int n, m;

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

II F[maxn];

int  main()
{
//  freopen("in.txt", "r", stdin);
    E = 0; ms(last, -1); ms(f, -1);
    int u, v, c;
    gi(n); gi(m);
    Rep(run, m){
        gi(u); gi(v); gi(c);
        add(u, v, c);
    }

    Rep(i, maxn){
        F[i] = mp(-1, -1);
    }

    f[1] = 0; d[1] = 0;
    int size = 0, size1;
    que[size++] = 1;

    int run = 0;
    while(size){
        run++;
        size1 = 0;
        Rep(i, size){
            que1[size1++] = que[i];
        }
        size = 0;
        Rep(i, size1){
            int u = que1[i];
            for(int e = last[u]; e != -1; e = next[e]){
                v = adj[e];
                if(f[v] > -1) continue;
                if(F[v].fi == -1){
                    F[v] = mp(d[u], color[e]);
                    que[size++] = v;
                    back[v] = u;
                    Color[v] = color[e];
                }
                else if(F[v] > mp(d[u], color[e])){
                    F[v] = mp(d[u], color[e]);
                    back[v] = u;
                    Color[v] = color[e];
                }
            }
        }
        int size2 = 0;
        Rep(i, size){
            u = que[i];
            f[u] = run;
            T[size2++] = triple(u, d[back[u]], Color[u]);
        }
        sort(T, T + size2);
        int R = 0;
        d[T[0].id] = R;
        For(i, 1, size2 - 1){
            if(T[i - 1] < T[i]) R++;
            d[T[i].id] = R;
        }
    }

    cout << f[n] << endl;
    u = n;
    size = 0;
    Rep(i, f[n]) {que[size++] = Color[u]; u = back[u];}
    for(int i = size - 1; i >= 0; i--){
        printf("%d%c", que[i], i == 0 ? '\n' : ' ');
    }
    return 0;
}

Code mẫu của skyvn97

#include<cstdio>
#include<cstring>
#include<queue>
#include<vector>
#define MAX   100100
#define FOR(i,a,b) for (int i=(a);i<=(b);i=i+1)
#define REP(i,n) for (int i=0;i<(n);i=i+1)
#define FORE(i,v) for (__typeof((v).begin()) i=(v).begin();i!=(v).end();i++)
#define fi   first
#define se   second
using namespace std;
const int INF=(int)1e9+7;
typedef pair<int,int> ii;
vector<ii> g[MAX];
int d[MAX];
bool p[MAX];
int m,n,md;
void minimize(int &x,const int &y) {
    if (x>y) x=y;
}
void loadgraph(void) {
    scanf("%d",&n);
    scanf("%d",&m);
    int u,v,c;
    REP(i,m) {
        scanf("%d",&u);
        scanf("%d",&v);
        scanf("%d",&c);
        g[u].push_back(ii(v,c));
        g[v].push_back(ii(u,c));
    }
}
void BFS(void) {
    queue<int> q;
    while (!q.empty()) q.pop();
    memset(d,-1,sizeof d);
    q.push(n);
    d[n]=0;
    while (!q.empty()) {
        int u=q.front();q.pop();
        FORE(it,g[u]) if (d[it->fi]<0) {
            d[it->fi]=d[u]+1;
            q.push(it->fi);
        }
    }
    printf("%d\n",d[1]);
    md=d[1];
}
void trace(void) {
    vector<int> t[3];
    REP(i,2) t[i].clear();
    t[0].push_back(1);
    REP(step,md) {
        int best=INF;
        FORE(it,t[step%2]) FORE(jt,g[*it])
            if (d[jt->fi]==md-step-1) minimize(best,jt->se);
        printf("%d",best);
        if (step<md-1) printf(" ");
        t[1-step%2].clear();
        FORE(it,t[step%2]) FORE(jt,g[*it])
            if (!p[jt->fi] && d[jt->fi]==md-step-1 && jt->se==best) {
                p[jt->fi]=true;
                t[1-step%2].push_back(jt->fi);
            }
    }
}
int main(void) {
    loadgraph();
    BFS();
    trace();
    return 0;
}