Problem p02685 (C++) — buggy submission, verdict: Runtime Error

// Hail god Yato

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

#define hs                                                                     \\
  ios::sync_with_stdio(0);                                                     \\
  cin.tie(0);                                                                  \\
  cout.tie(0);
typedef long long ll;
const ll MOD = 998244353;
const ll INF = 1e18;
const ll MAX = 200008;
//
//

struct mi {
  ll v;
  explicit operator ll() const { return v; }
  mi() { v = 0; }
  mi(ll _v) {
    v = (-MOD < _v && _v < MOD) ? _v : _v % MOD;
    if (v < 0)
      v += MOD;
  }
  friend bool operator==(const mi &a, const mi &b) { return a.v == b.v; }
  friend bool operator!=(const mi &a, const mi &b) { return !(a == b); }
  friend bool operator<(const mi &a, const mi &b) { return a.v < b.v; }

  mi &operator+=(const mi &m) {
    if ((v += m.v) >= MOD)
      v -= MOD;
    return *this;
  }
  mi &operator-=(const mi &m) {
    if ((v -= m.v) < 0)
      v += MOD;
    return *this;
  }
  mi &operator*=(const mi &m) {
    v = v * m.v % MOD;
    return *this;
  }
  mi &operator/=(const mi &m) { return (*this) *= inv(m); }
  friend mi pow(mi a, ll p) {
    mi ans = 1;
    assert(p >= 0);
    for (; p; p /= 2, a *= a)
      if (p & 1)
        ans *= a;
    return ans;
  }
  friend mi inv(const mi &a) {
    assert(a.v != 0);
    return pow(a, MOD - 2);
  }

  mi operator-() const { return mi(-v); }
  mi &operator++() { return *this += 1; }
  mi &operator--() { return *this -= 1; }
  mi operator++(int) {
    mi temp;
    temp.v = v++;
    return temp;
  }
  mi operator--(int) {
    mi temp;
    temp.v = v--;
    return temp;
  }
  friend mi operator+(mi a, const mi &b) { return a += b; }
  friend mi operator-(mi a, const mi &b) { return a -= b; }
  friend mi operator*(mi a, const mi &b) { return a *= b; }
  friend mi operator/(mi a, const mi &b) { return a /= b; }
  friend ostream &operator<<(ostream &os, const mi &m) {
    os << m.v;
    return os;
  }
  friend istream &operator>>(istream &is, mi &m) {
    ll x;
    is >> x;
    m.v = x;
    return is;
  }
};

typedef vector<mi> vmi;
typedef pair<mi, mi> pmi;
typedef vector<pmi> vpmi;
mi facs[MAX];
mi facInvs[MAX];

mi choose(mi _a, mi _b) {
  ll a = (ll)_a, b = (ll)_b;
  if (b > a)
    return 0;
  if (a < 0)
    return 0;
  if (b < 0)
    return 0;
  mi cur = facs[a];
  cur = cur * facInvs[b];
  cur = cur * facInvs[a - b];
  return cur;
}

void initFacs() {
  facs[0] = 1;
  facInvs[0] = 1;
  for (int i = 1; i < MAX; i++) {
    facs[i] = (facs[i - 1] * i);
    facInvs[i] = inv(facs[i]);
  }
}

void solve() {
  ll n, m, k;
  cin >> n >> m >> k;
  initFacs();
  mi ans = 0;
  mi mm = m;
  for (int i = 0; i <= k; i++) {
    ans += m * choose(n - 1, i) * pow(1, k) * pow(mm - 1, n - 1 - i);
  }
  cout << ans;
}
int main() {
  hs;
  ll t;
  t = 1;
  // cin>>t;
  for (int i = 1; i <= t; i++) {
    // cout<<"Case #"<<i<<": ";
    solve();
  }
  return 0;
}

Error: WA

Fixed submission:

// Hail god Yato

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

#define hs                                                                     \\
  ios::sync_with_stdio(0);                                                     \\
  cin.tie(0);                                                                  \\
  cout.tie(0);
typedef long long ll;
const ll MOD = 998244353;
const ll INF = 1e18;
const ll MAX = 100001;
//
//

struct mi {
  ll v;
  explicit operator ll() const { return v; }
  mi() { v = 0; }
  mi(ll _v) {
    v = (-MOD < _v && _v < MOD) ? _v : _v % MOD;
    if (v < 0)
      v += MOD;
  }
  friend bool operator==(const mi &a, const mi &b) { return a.v == b.v; }
  friend bool operator!=(const mi &a, const mi &b) { return !(a == b); }
  friend bool operator<(const mi &a, const mi &b) { return a.v < b.v; }

  mi &operator+=(const mi &m) {
    if ((v += m.v) >= MOD)
      v -= MOD;
    return *this;
  }
  mi &operator-=(const mi &m) {
    if ((v -= m.v) < 0)
      v += MOD;
    return *this;
  }
  mi &operator*=(const mi &m) {
    v = v * m.v % MOD;
    return *this;
  }
  mi &operator/=(const mi &m) { return (*this) *= inv(m); }
  friend mi pow(mi a, ll p) {
    mi ans = 1;
    assert(p >= 0);
    for (; p; p /= 2, a *= a)
      if (p & 1)
        ans *= a;
    return ans;
  }
  friend mi inv(const mi &a) {
    assert(a.v != 0);
    return pow(a, MOD - 2);
  }

  mi operator-() const { return mi(-v); }
  mi &operator++() { return *this += 1; }
  mi &operator--() { return *this -= 1; }
  mi operator++(int) {
    mi temp;
    temp.v = v++;
    return temp;
  }
  mi operator--(int) {
    mi temp;
    temp.v = v--;
    return temp;
  }
  friend mi operator+(mi a, const mi &b) { return a += b; }
  friend mi operator-(mi a, const mi &b) { return a -= b; }
  friend mi operator*(mi a, const mi &b) { return a *= b; }
  friend mi operator/(mi a, const mi &b) { return a /= b; }
  friend ostream &operator<<(ostream &os, const mi &m) {
    os << m.v;
    return os;
  }
  friend istream &operator>>(istream &is, mi &m) {
    ll x;
    is >> x;
    m.v = x;
    return is;
  }
};

typedef vector<mi> vmi;
typedef pair<mi, mi> pmi;
typedef vector<pmi> vpmi;
mi facs[MAX];
mi facInvs[MAX];

mi choose(mi _a, mi _b) {
  ll a = (ll)_a, b = (ll)_b;
  if (b > a)
    return 0;
  if (a < 0)
    return 0;
  if (b < 0)
    return 0;
  mi cur = facs[a];
  cur = cur * facInvs[b];
  cur = cur * facInvs[a - b];
  return cur;
}

void initFacs() {
  facs[0] = 1;
  facInvs[0] = 1;
  for (int i = 1; i < MAX; i++) {
    facs[i] = (facs[i - 1] * i);
    facInvs[i] = inv(facs[i]);
  }
}

void solve() {
  ll n, m, k;
  cin >> n >> m >> k;
  initFacs();
  mi ans = 0;
  mi mm = m;
  for (int i = 0; i <= k; i++) {
    ans += m * choose(n - 1, i) * pow(1, k) * pow(mm - 1, n - 1 - i);
  }
  cout << ans;
}
int main() {
  hs;
  ll t;
  t = 1;
  // cin>>t;
  for (int i = 1; i <= t; i++) {
    // cout<<"Case #"<<i<<": ";
    solve();
  }
  return 0;
}