Distinct Routes

#include <bits/stdc++.h>

using namespace std;

const int N = 5e2 + 5;

int n, m;
vector<int> g[N];
int cap[N][N];
int p[N];
vector<vector<int>> res;

int find_flow(int a, int b) {
  memset(p, -1, sizeof(p));
  p[a] = -2;
  queue<pair<int, int> > q;
  q.push(make_pair(a, 1));
  while (!q.empty()) {
    int u = q.front().first;
    int f = q.front().second;
    q.pop();
    for (int v : g[u]) {
      if (p[v] == -1 && cap[u][v] > 0) {
        p[v] = u;
        int nf = min(f, cap[u][v]);
        if (v == b) {
          return nf;
        }
        q.push(make_pair(v, nf));
      }
    }
  }
  return 0;
}

void max_flow(int a, int b) {
  int flow = find_flow(a, b);
  int ans = 0;
  while (flow > 0) {
    vector<int> add;
    ans += flow;
    int s = b;
    while (s != a) {
      add.emplace_back(s);
      cap[p[s]][s] -= flow;
      cap[s][p[s]] += flow;
      s = p[s];
    }
    add.emplace_back(a);
    reverse(add.begin(), add.end());
    res.emplace_back(add);
    flow = find_flow(a, b);
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> n >> m;
  for (int i = 1; i <= m; i++) {
    int a, b;
    cin >> a >> b;
    g[a].emplace_back(b);
    g[b].emplace_back(a);
    cap[a][b] = 1;
  }
  max_flow(1, n);
  cout << res.size() << '\n';
  for (auto x : res) {
    cout << x.size() << '\n';
    for (int y : x) {
      cout << y << ' ';
    }
    cout << '\n';
  }
  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: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: WRONG ANSWER