Problem p02632 (C++) — buggy submission, verdict: Runtime Error

#line 2 "codes/header.hpp"

//%snippet.set('header')%
//%snippet.fold()%
#ifndef HEADER_H
#define HEADER_H

// template version 2.0
using namespace std;
#include <bits/stdc++.h>

// varibable settings
const long long INF = 1e18;
template <class T> constexpr T inf = numeric_limits<T>::max() / 2.1;

#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (ll i = (ll)((b)-1); i >= (ll)(a); --i)
#define r_rep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define mt(...) make_tuple(__VA_ARGS__)
#define ub upper_bound
#define lb lower_bound
#define lpos(A, x) (lower_bound(all(A), x) - A.begin())
#define upos(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) {
  if ((a) < (b))
    (a) = (b);
}
template <class T> inline void chmin(T &a, const T &b) {
  if ((a) > (b))
    (a) = (b);
}
template <typename X, typename T> auto make_table(X x, T a) {
  return vector<T>(x, a);
}
template <typename X, typename Y, typename Z, typename... Zs>
auto make_table(X x, Y y, Z z, Zs... zs) {
  auto cont = make_table(y, z, zs...);
  return vector<decltype(cont)>(x, cont);
}

#define cdiv(a, b) (((a) + (b)-1) / (b))
#define is_in(x, a, b) ((a) <= (x) && (x) < (b))
#define uni(x)                                                                 \\
  sort(all(x));                                                                \\
  x.erase(unique(all(x)), x.end())
#define slice(l, r) substr(l, r - l)

typedef long long ll;
typedef long double ld;
using vl = vector<ll>;
using vvl = vector<vl>;
using pll = pair<ll, ll>;

template <typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
void check_input() {
  assert(cin.eof() == 0);
  int tmp;
  cin >> tmp;
  assert(cin.eof() == 1);
}

#if defined(PCM) || defined(LOCAL)
#else
#define dump(...) ;
#define dump_1d(...) ;
#define dump_2d(...) ;
#define cerrendl ;
#endif

#endif /* HEADER_H */
//%snippet.end()%
#line 2 "codes/solve.cpp"
template <class T = ll> using vec = vector<T>;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

int mod = 1e9 + 7;
struct mint { //{{{
  ll x;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}

  // ?= operator
  mint &operator+=(const mint a) {
    (x += a.x) %= mod;
    return *this;
  }
  mint &operator-=(const mint a) {
    (x += mod - a.x) %= mod;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint &operator/=(const mint &rhs) {
    if (rhs.x == 0)
      throw runtime_error("mint zero division");
    return *this *= rhs.inv();
  }

  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }

  mint pow(int n) const {
    mint res(1), x(*this);
    if (n < 0) {
      n = -n;
      x = (*this).inv();
    }
    while (n) {
      if (n & 1)
        res *= x;
      x *= x;
      n >>= 1;
    }
    return res;
  }

  mint inv() const {
    if (x == 0)
      throw runtime_error("inv does not exist");
    return pow(mod - 2);
  }
  // mint inv()const{
  //     int x,y;
  //     int g=extgcd(v,mod,x,y);
  //     assert(g==1);
  //     if(x<0)x+=mod;
  //     return mint(x);
  // }

  bool operator<(const mint &r) const { return x < r.x; }
  bool operator==(const mint &r) const { return x == r.x; }
};
istream &operator>>(istream &is, const mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }
//}}}

struct combination { // {{{
  vector<mint> fact, ifact;
  combination(int n) : fact(n + 1), ifact(n + 1) {
    assert(n < mod);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i)
      fact[i] = fact[i - 1] * i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i)
      ifact[i - 1] = ifact[i] * i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n)
      return 0;
    return fact[n] * ifact[k] * ifact[n - k];
  }
} // }}}
com(2000005);

int solve() {
  ll k;
  cin >> k;
  string s;
  cin >> s;
  ll n = sz(s);

  mint x = mint(26).pow(k);
  mint ans = x;
  rep(i, k) {
    x *= 25;
    x /= 26;
    x /= com(n + i - 1, n - 1);
    x *= com(n + i, n - 1);
    ans += x;
    // dump(ans);
  }
  cout << ans << endl;

  return 0;
}

int main() { /*{{{*/
  solve();
  check_input();
  return 0;
} /*}}}*/


Error: 0

Fixed submission:

#line 2 "codes/header.hpp"

//%snippet.set('header')%
//%snippet.fold()%
#ifndef HEADER_H
#define HEADER_H

// template version 2.0
using namespace std;
#include <bits/stdc++.h>

// varibable settings
const long long INF = 1e18;
template <class T> constexpr T inf = numeric_limits<T>::max() / 2.1;

#define _overload3(_1, _2, _3, name, ...) name
#define _rep(i, n) repi(i, 0, n)
#define repi(i, a, b) for (ll i = (ll)(a); i < (ll)(b); ++i)
#define rep(...) _overload3(__VA_ARGS__, repi, _rep, )(__VA_ARGS__)
#define _rrep(i, n) rrepi(i, 0, n)
#define rrepi(i, a, b) for (ll i = (ll)((b)-1); i >= (ll)(a); --i)
#define r_rep(...) _overload3(__VA_ARGS__, rrepi, _rrep, )(__VA_ARGS__)
#define each(i, a) for (auto &&i : a)
#define all(x) (x).begin(), (x).end()
#define sz(x) ((int)(x).size())
#define pb(a) push_back(a)
#define mp(a, b) make_pair(a, b)
#define mt(...) make_tuple(__VA_ARGS__)
#define ub upper_bound
#define lb lower_bound
#define lpos(A, x) (lower_bound(all(A), x) - A.begin())
#define upos(A, x) (upper_bound(all(A), x) - A.begin())
template <class T> inline void chmax(T &a, const T &b) {
  if ((a) < (b))
    (a) = (b);
}
template <class T> inline void chmin(T &a, const T &b) {
  if ((a) > (b))
    (a) = (b);
}
template <typename X, typename T> auto make_table(X x, T a) {
  return vector<T>(x, a);
}
template <typename X, typename Y, typename Z, typename... Zs>
auto make_table(X x, Y y, Z z, Zs... zs) {
  auto cont = make_table(y, z, zs...);
  return vector<decltype(cont)>(x, cont);
}

#define cdiv(a, b) (((a) + (b)-1) / (b))
#define is_in(x, a, b) ((a) <= (x) && (x) < (b))
#define uni(x)                                                                 \\
  sort(all(x));                                                                \\
  x.erase(unique(all(x)), x.end())
#define slice(l, r) substr(l, r - l)

typedef long long ll;
typedef long double ld;
using vl = vector<ll>;
using vvl = vector<vl>;
using pll = pair<ll, ll>;

template <typename T> using PQ = priority_queue<T, vector<T>, greater<T>>;
void check_input() {
  assert(cin.eof() == 0);
  int tmp;
  cin >> tmp;
  assert(cin.eof() == 1);
}

#if defined(PCM) || defined(LOCAL)
#else
#define dump(...) ;
#define dump_1d(...) ;
#define dump_2d(...) ;
#define cerrendl ;
#endif

#endif /* HEADER_H */
//%snippet.end()%
#line 2 "codes/solve.cpp"
template <class T = ll> using vec = vector<T>;
struct Fast {
  Fast() {
    std::cin.tie(0);
    ios::sync_with_stdio(false);
  }
} fast;

int mod = 1e9 + 7;
struct mint { //{{{
  ll x;
  mint(ll x = 0) : x((x % mod + mod) % mod) {}

  // ?= operator
  mint &operator+=(const mint a) {
    (x += a.x) %= mod;
    return *this;
  }
  mint &operator-=(const mint a) {
    (x += mod - a.x) %= mod;
    return *this;
  }
  mint &operator*=(const mint a) {
    (x *= a.x) %= mod;
    return *this;
  }
  mint &operator/=(const mint &rhs) {
    if (rhs.x == 0)
      throw runtime_error("mint zero division");
    return *this *= rhs.inv();
  }

  mint operator+(const mint a) const {
    mint res(*this);
    return res += a;
  }
  mint operator-(const mint a) const {
    mint res(*this);
    return res -= a;
  }
  mint operator*(const mint a) const {
    mint res(*this);
    return res *= a;
  }
  mint operator/(const mint a) const {
    mint res(*this);
    return res /= a;
  }

  mint pow(int n) const {
    mint res(1), x(*this);
    if (n < 0) {
      n = -n;
      x = (*this).inv();
    }
    while (n) {
      if (n & 1)
        res *= x;
      x *= x;
      n >>= 1;
    }
    return res;
  }

  mint inv() const {
    if (x == 0)
      throw runtime_error("inv does not exist");
    return pow(mod - 2);
  }
  // mint inv()const{
  //     int x,y;
  //     int g=extgcd(v,mod,x,y);
  //     assert(g==1);
  //     if(x<0)x+=mod;
  //     return mint(x);
  // }

  bool operator<(const mint &r) const { return x < r.x; }
  bool operator==(const mint &r) const { return x == r.x; }
};
istream &operator>>(istream &is, const mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }
//}}}

struct combination { // {{{
  vector<mint> fact, ifact;
  combination(int n) : fact(n + 1), ifact(n + 1) {
    assert(n < mod);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i)
      fact[i] = fact[i - 1] * i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i)
      ifact[i - 1] = ifact[i] * i;
  }
  mint operator()(int n, int k) {
    if (k < 0 || k > n)
      return 0;
    return fact[n] * ifact[k] * ifact[n - k];
  }
} // }}}
com(500001);

int solve() {
  int k;
  cin >> k;
  string s;
  cin >> s;
  int n = sz(s);

  mint x = mint(26).pow(k);
  mint ans = x;
  rep(i, k) {
    x *= 25;
    x /= 26;
    x /= com(n + i - 1, n - 1);
    x *= com(n + i, n - 1);
    ans += x;
    dump(ans);
  }
  cout << ans << endl;

  return 0;
}

int main() { /*{{{*/
  solve();
  check_input();
  return 0;
} /*}}}*/