Problem p01230 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
#define FOR(i, k, n) for (int i = (int)(k); i < (int)(n); i++)
#define REP(i, n) FOR(i, 0, n)
#define ALL(a) a.begin(), a.end()
#define MS(m, v) memset(m, v, sizeof(m))
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> pii;
const int MOD = 1000000007;
const int INF = MOD + 1;
const ld EPS = 1e-12;
template <class T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <class T> T &chmax(T &a, const T &b) { return a = max(a, b); }

/*--------------------template--------------------*/

typedef ll Data;
typedef vector<Data> Array;
typedef vector<Array> Matrix;

bool is_zero(Data dat) { return (abs(dat) < EPS); }

Matrix operator-(Matrix mat) {
  REP(i, mat.size()) REP(j, mat[0].size()) mat[i][j] = -mat[i][j];
  return mat;
}

Matrix operator+(Matrix lhs, const Matrix &rhs) {
  REP(i, lhs.size()) REP(j, lhs[0].size()) lhs[i][j] = lhs[i][j] + rhs[i][j];
  return lhs;
}

Matrix operator-(Matrix lhs, const Matrix &rhs) {
  REP(i, lhs.size()) REP(j, lhs[0].size()) lhs[i][j] = lhs[i][j] - rhs[i][j];
  return lhs;
}

Matrix operator*(const Matrix &lhs, const Matrix &rhs) {
  Matrix res(lhs.size(), Array(rhs[0].size(), 0));
  REP(i, lhs.size())
  REP(j, rhs[0].size()) REP(k, rhs.size()) res[i][j] =
      fma(lhs[i][k], rhs[k][j], res[i][j]);
  return res;
}

Array operator+(const Array &lhs, const Array &rhs) {
  Array res = lhs;
  REP(i, rhs.size()) res[i] = res[i] + rhs[i];
  return res;
}

Array operator*(const Matrix &lhs, const Array &rhs) {
  Array res(lhs.size());
  REP(i, lhs.size())
  res[i] = inner_product(begin(lhs[i]), end(lhs[i]), begin(rhs), Data(0));
  return res;
}

Array operator*(Data scalar, const Array &rhs) {
  Array res(rhs.size());
  REP(i, rhs.size())
  res[i] = scalar * rhs[i];
  return res;
}

Matrix transpose(const Matrix &A) {
  const ll n = A[0].size(), m = A.size();
  Matrix res(n, Array(m, 0));
  REP(i, n) REP(j, m) res[i][j] = A[j][i];
  return res;
}

Data inner_product_ex(const Array &a, const Array &b, const Matrix &m) {
  Array b_prime = m * b;
  return inner_product(begin(a), end(a), begin(b_prime), Data(0));
}

Data norm(const Array &a) {
  return inner_product(begin(a), end(a), begin(a), Data(0));
}

Data norm(const Array &a, const Matrix &M) { return inner_product_ex(a, a, M); }

ll rankMat(Matrix A) {
  const ll n = A.size(), m = A[0].size();
  ll r = 0;
  for (ll i = 0; r < n && i < m; ++i) {
    ll pivot = r;
    for (ll j = r + 1; j < n; ++j)
      if (abs(A[j][i]) > abs(A[pivot][i]))
        pivot = j;
    swap(A[pivot], A[r]);
    if (is_zero(A[r][i]))
      continue;
    for (ll k = m - 1; k >= i; --k)
      A[r][k] = A[r][k] / A[r][i];
    for (ll j = r + 1; j < n; ++j)
      for (ll k = m - 1; k >= i; --k)
        A[j][k] = fma(-A[r][k], A[j][i], A[j][k]);
    ++r;
  }
  return r;
}

Data det(Matrix A) {
  const ll n = A.size();
  Data D = Data(1);
  for (ll i = 0; i < n; ++i) {
    ll pivot = i;
    for (ll j = i + 1; j < n; ++j)
      if (abs(A[j][i]) > abs(A[pivot][i]))
        pivot = j;
    swap(A[pivot], A[i]);
    D = D * A[i][i] * Data(i != pivot ? -1 : 1);
    if (is_zero(A[i][i]))
      break;
    for (ll j = i + 1; j < n; ++j)
      for (ll k = n - 1; k >= i; --k)
        A[j][k] = A[j][k] - A[i][k] * A[j][i] / A[i][i];
  }
  return D;
}

Matrix pow(Matrix x, ll n) {
  ll sz = x.size();
  Matrix res(sz, Array(sz));
  REP(i, sz) res[i][i] = 1;
  while (n > 0) {
    if (n & 1)
      res = res * x;
    x = x * x;
    n >>= 1;
  }
  return res;
}

void output(bool f) { cout << (f ? "yes" : "no") << endl; }

ll n, m, z;
map<pii, ll> mp;

int main() {
  cin.sync_with_stdio(false);
  cout << fixed << setprecision(10);
  while (cin >> n >> m >> z, n) {
    vector<vi> node(n);
    REP(i, m) {
      ll a, b;
      cin >> a >> b;
      a--;
      b--;
      if (b == 0)
        swap(a, b);
      mp[pii(b, a)] = 1 + i * 2;
      node[a].push_back(1 + i * 2);
      mp[pii(a, b)] = 2 + i * 2;
      node[b].push_back(2 + i * 2);
    }
    ll nn = mp.size() + 1;
    Matrix mat(nn, Array(nn));
    for (auto e : mp) {
      ll from = e.first.first, to = e.first.second;
      if (from == 0) {
        mat[0][mp[pii(from, to)]] = 1;
      }
      for (auto i : node[from]) {
        if (i == mp[pii(to, from)])
          continue;
        mat[i][mp[pii(from, to)]] = 1;
      }
    }
    Matrix ans(1, Array(nn));
    ans[0][0] = 1;
    ans = ans * pow(mat, z);
    bool f = false;
    for (auto i : node[n - 1]) {
      if (ans[0][i])
        f = true;
    }
    output(f);
  }
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define FOR(i, k, n) for (int i = (int)(k); i < (int)(n); i++)
#define REP(i, n) FOR(i, 0, n)
#define ALL(a) a.begin(), a.end()
#define MS(m, v) memset(m, v, sizeof(m))
typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> pii;
const int MOD = 1000000007;
const int INF = MOD + 1;
const ld EPS = 1e-12;
template <class T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <class T> T &chmax(T &a, const T &b) { return a = max(a, b); }

/*--------------------template--------------------*/

typedef ll Data;
typedef vector<Data> Array;
typedef vector<Array> Matrix;

bool is_zero(Data dat) { return (abs(dat) < EPS); }

Matrix operator-(Matrix mat) {
  REP(i, mat.size()) REP(j, mat[0].size()) mat[i][j] = -mat[i][j];
  return mat;
}

Matrix operator+(Matrix lhs, const Matrix &rhs) {
  REP(i, lhs.size()) REP(j, lhs[0].size()) lhs[i][j] = lhs[i][j] + rhs[i][j];
  return lhs;
}

Matrix operator-(Matrix lhs, const Matrix &rhs) {
  REP(i, lhs.size()) REP(j, lhs[0].size()) lhs[i][j] = lhs[i][j] - rhs[i][j];
  return lhs;
}

Matrix operator*(const Matrix &lhs, const Matrix &rhs) {
  Matrix res(lhs.size(), Array(rhs[0].size(), 0));
  REP(i, lhs.size())
  REP(j, rhs[0].size()) REP(k, rhs.size()) res[i][j] =
      fma(lhs[i][k], rhs[k][j], res[i][j]);
  return res;
}

Array operator+(const Array &lhs, const Array &rhs) {
  Array res = lhs;
  REP(i, rhs.size()) res[i] = res[i] + rhs[i];
  return res;
}

Array operator*(const Matrix &lhs, const Array &rhs) {
  Array res(lhs.size());
  REP(i, lhs.size())
  res[i] = inner_product(begin(lhs[i]), end(lhs[i]), begin(rhs), Data(0));
  return res;
}

Array operator*(Data scalar, const Array &rhs) {
  Array res(rhs.size());
  REP(i, rhs.size())
  res[i] = scalar * rhs[i];
  return res;
}

Matrix transpose(const Matrix &A) {
  const ll n = A[0].size(), m = A.size();
  Matrix res(n, Array(m, 0));
  REP(i, n) REP(j, m) res[i][j] = A[j][i];
  return res;
}

Data inner_product_ex(const Array &a, const Array &b, const Matrix &m) {
  Array b_prime = m * b;
  return inner_product(begin(a), end(a), begin(b_prime), Data(0));
}

Data norm(const Array &a) {
  return inner_product(begin(a), end(a), begin(a), Data(0));
}

Data norm(const Array &a, const Matrix &M) { return inner_product_ex(a, a, M); }

ll rankMat(Matrix A) {
  const ll n = A.size(), m = A[0].size();
  ll r = 0;
  for (ll i = 0; r < n && i < m; ++i) {
    ll pivot = r;
    for (ll j = r + 1; j < n; ++j)
      if (abs(A[j][i]) > abs(A[pivot][i]))
        pivot = j;
    swap(A[pivot], A[r]);
    if (is_zero(A[r][i]))
      continue;
    for (ll k = m - 1; k >= i; --k)
      A[r][k] = A[r][k] / A[r][i];
    for (ll j = r + 1; j < n; ++j)
      for (ll k = m - 1; k >= i; --k)
        A[j][k] = fma(-A[r][k], A[j][i], A[j][k]);
    ++r;
  }
  return r;
}

Data det(Matrix A) {
  const ll n = A.size();
  Data D = Data(1);
  for (ll i = 0; i < n; ++i) {
    ll pivot = i;
    for (ll j = i + 1; j < n; ++j)
      if (abs(A[j][i]) > abs(A[pivot][i]))
        pivot = j;
    swap(A[pivot], A[i]);
    D = D * A[i][i] * Data(i != pivot ? -1 : 1);
    if (is_zero(A[i][i]))
      break;
    for (ll j = i + 1; j < n; ++j)
      for (ll k = n - 1; k >= i; --k)
        A[j][k] = A[j][k] - A[i][k] * A[j][i] / A[i][i];
  }
  return D;
}

Matrix pow(Matrix x, ll n) {
  ll sz = x.size();
  Matrix res(sz, Array(sz));
  REP(i, sz) res[i][i] = 1;
  while (n > 0) {
    if (n & 1)
      res = res * x;
    x = x * x;
    n >>= 1;
  }
  return res;
}

void output(bool f) { cout << (f ? "yes" : "no") << endl; }

ll n, m, z;
map<pii, ll> mp;

int main() {
  cin.sync_with_stdio(false);
  cout << fixed << setprecision(10);
  while (cin >> n >> m >> z, n) {
    mp.clear();
    vector<vi> node(n);
    REP(i, m) {
      ll a, b;
      cin >> a >> b;
      a--;
      b--;
      if (b == 0)
        swap(a, b);
      mp[pii(b, a)] = 1 + i * 2;
      node[a].push_back(1 + i * 2);
      mp[pii(a, b)] = 2 + i * 2;
      node[b].push_back(2 + i * 2);
    }
    ll nn = mp.size() + 1;
    Matrix mat(nn, Array(nn));
    for (auto e : mp) {
      ll from = e.first.first, to = e.first.second;
      if (from == 0) {
        mat[0][mp[pii(from, to)]] = 1;
      }
      for (auto i : node[from]) {
        if (i == mp[pii(to, from)])
          continue;
        mat[i][mp[pii(from, to)]] = 1;
      }
    }
    Matrix ans(1, Array(nn));
    ans[0][0] = 1;
    ans = ans * pow(mat, z);
    bool f = false;
    for (auto i : node[n - 1]) {
      if (ans[0][i])
        f = true;
    }
    output(f);
  }
  return 0;
}