Distinct Routes

#include <bits/stdc++.h>
using namespace std;

// debug
template<class T> ostream& operator<<(ostream&, const vector<T>&);
template<class T> ostream& operator<<(ostream&, const set<T>&);
template<class T> ostream& operator<<(ostream&, const multiset<T>&);
template<class K, class V> ostream& operator<<(ostream&, const map<K, V>&);
template<class T, size_t N> ostream& operator<<(ostream&, const array<T, N>&);
template<class A, class B> ostream& operator<<(ostream& os, const pair<A, B>& p) { return os << "(" << p.first << ", " << p.second << ")"; }
template<class T>
void print_collection(ostream& os, const T& v) {
    os << "{";
    bool first = true;
    for (const auto& x : v) {
        if (!first) os << ", ";
        first = false;
        os << x;
    }
    os << "}";
}
template<class T> ostream& operator<<(ostream& os, const vector<T>& v) { print_collection(os, v); return os; }
template<class T> ostream& operator<<(ostream& os, const set<T>& v) { print_collection(os, v); return os; }
template<class T> ostream& operator<<(ostream& os, const multiset<T>& v) { print_collection(os, v); return os; }
template<class K, class V> ostream& operator<<(ostream& os, const map<K, V>& v) { print_collection(os, v); return os; }
template<class T, size_t N> ostream& operator<<(ostream& os, const array<T, N>& v) { print_collection(os, v); return os; }
#define dbg(x) cerr << #x << " = " << (x) << '\n'

using ll = long long;
constexpr int INF = 1'000'000'000; // 1e9
constexpr ll LINF = 1'000'000'000'000'000'000LL; // 1e18
constexpr int MOD = 1'000'000'007; // 1e9 + 7

inline ll add(ll a, ll b) { return (a + b) % MOD; }
inline ll sub(ll a, ll b) { return ((a - b) % MOD + MOD) % MOD; }
inline ll mul(ll a, ll b) { return (a * b) % MOD; }


void solve() {
    int N, M;
    cin >> N >> M;

    vector<vector<int>> adj(N + 1);
    vector<vector<int>> ad(N+1);
    vector<vector<ll>> cap(N + 1, vector<ll>(N + 1, 0));

    for (int i = 0; i < M; i++) {
        int a, b;
        cin >> a >> b;

        adj[a].push_back(b);
        adj[b].push_back(a);

        ad[a].push_back(b);

        cap[a][b] += 1;
    }

    vector<char> visited(N + 1, 0);

    auto dfs = [&](auto&& dfs, int u, ll pushed) -> ll {
        if (u == N) return pushed;

        visited[u] = 1;

        for (int v : adj[u]) {
            if (visited[v]) continue;

            ll f = dfs(dfs, v, min(pushed, cap[u][v]));

            if (f > 0) {
                cap[u][v] -= f;
                cap[v][u] += f;
                return f;
            }
        }

        return 0;
    };

    ll flow = 0;
    while (true) {
        fill(visited.begin(), visited.end(), 0);

        ll pushed = dfs(dfs, 1, LINF);

        if (pushed == 0) break;

        flow += pushed;
    }

    cout << flow << '\n';


    while (flow-- > 0) {
        vector<char> visited(N + 1, 0);
        vector<int> path;

        auto dfs = [&](auto&& dfs, int u) -> bool {
            if (u == N) {
                return true;
            }

            visited[u] = 1;

            for (auto &v: ad[u]) {
                if (v == -1 || visited[v]) continue;

                bool f = dfs(dfs, v);

                if (f) {
                    path.push_back(v);
                    v = -1;
                    return f;
                }
            }

            return false;
        };

        dfs(dfs, 1);

        cout << path.size() + 1 << "\n1";

        for(int i = path.size() - 1; i >= 0; i--) {
            cout << " " << path[i];
        }

        cout << "\n";
    }

    //     ll flow = 0;
    // while (true) {
    //     fill(visited.begin(), visited.end(), 0);

    //     ll pushed = dfs(dfs, 1, LINF);

    //     if (pushed == 0) break;

    //     flow += pushed;
    // }

    // cout << flow << '\n';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    solve();

    return 0;
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: WRONG ANSWER

Test 7

Verdict: WRONG ANSWER

Test 8

Verdict: WRONG ANSWER

Test 9

Verdict: ACCEPTED

Test 10

Verdict: WRONG ANSWER

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: ACCEPTED

Test 13

Verdict: WRONG ANSWER

Test 14

Verdict: WRONG ANSWER

Test 15

Verdict: WRONG ANSWER