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

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

#define NDEBUG
#include <cassert>

typedef long long ll;
typedef long double Double;
typedef unsigned long long ull;
typedef pair<int, int> ii;
typedef pair<ll, ll> llll;
typedef pair<double, double> dd;

typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<llll> vllll;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<long double> vD;

#define sz(a) int((a).size())
#define pb push_back
#define eb emplace_back
#define FOR(var, from, to) for (int var = (from); var <= (to); ++var)
#define rep(var, n) for (int var = 0; var < (n); ++var)
#define rep1(var, n) for (int var = 1; var <= (n); ++var)
#define repC2(vari, varj, n)                                                   \\
  for (int vari = 0; vari < (n)-1; ++vari)                                     \\
    for (int varj = vari + 1; varj < (n); ++varj)
#define repC3(vari, varj, vark, n)                                             \\
  for (int vari = 0; vari < (n)-2; ++vari)                                     \\
    for (int varj = vari + 1; varj < (n)-1; ++varj)                            \\
      for (int vark = varj + 1; vark < (n); ++vark)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define tr(i, c) for (auto i = (c).begin(); i != (c).end(); ++i)
#define found(s, e) ((s).find(e) != (s).end())
#define mset(arr, val) memset(arr, val, sizeof(arr))
#define mid(x, y) ((x) + ((y) - (x)) / 2)
#define IN(x, a, b) ((a) <= (x) && (x) <= (b))
#define cons make_pair
#define clamp(v, lo, hi) min(max(v, lo), hi)
#define ABS(x) max((x), -(x))
#define PQ(T) priority_queue<T, vector<T>, greater<T>>

template <typename T1, typename T2> inline void amin(T1 &a, T2 const &b) {
  if (a > b)
    a = b;
}
template <typename T1, typename T2> inline void amax(T1 &a, T2 const &b) {
  if (a < b)
    a = b;
}
template <typename X, typename T> auto vectors(X x, T a) {
  return vector<T>(x, a);
}
template <typename X, typename Y, typename Z, typename... Zs>
auto vectors(X x, Y y, Z z, Zs... zs) {
  auto cont = vectors(y, z, zs...);
  return vector<decltype(cont)>(x, cont);
}

inline ll square(ll x) { return x * x; }
inline ll gcd(ll a, ll b) {
  while (a)
    swap(a, b %= a);
  return b;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template <typename T> inline T mod(T a, T b) { return ((a % b) + b) % b; }

template <typename T> int find_left(vector<T> &v, T elem) {
  return (int)(upper_bound(v.begin(), v.end(), elem) - v.begin()) - 1;
}
template <typename T> int find_right(vector<T> &v, T elem) {
  return (int)(lower_bound(v.begin(), v.end(), elem) - v.begin());
}

const ll MOD = 1000000007LL;

inline ll ADD(ll x, ll y) { return (x + y) % MOD; }
inline ll SUB(ll x, ll y) { return (x - y + MOD) % MOD; }
inline ll MUL(ll x, ll y) { return x * y % MOD; }
inline ll POW(ll x, ll e) {
  ll v = 1;
  for (; e; x = MUL(x, x), e >>= 1)
    if (e & 1)
      v = MUL(v, x);
  return v;
}
inline ll INV(ll y) { /*assert(y%MOD!=0);*/
  return POW(y, MOD - 2);
}
inline ll DIV(ll x, ll y) { return MUL(x, INV(y)); }
ll comb(ll n, ll k) {
  ll v = 1;
  for (ll i = 1; i <= k; i++)
    v = DIV(MUL(v, n - i + 1), i);
  return v;
}

#define INTSPACE 12
char _buf[INTSPACE * 1000000 + 3];

int loadint() {
  if (fgets(_buf, INTSPACE + 3, stdin) == NULL)
    return 0;
  return atoi(_buf);
}

int loadvec(vector<int> &v, int N = -1) {
  if (N == 0) {
    v.clear();
    return 0;
  }
  if (N == -1) {
    N = loadint();
    if (N == 0)
      return 0;
  }
  int bufsize = INTSPACE * N + 3;
  if (fgets(_buf, bufsize, stdin) == NULL)
    return 0;
  v.resize(N);

  int i = 0;
  bool last = false;
  for (char *p = &_buf[0];;) {
    char *q = p;
    while (*q > ' ')
      ++q;
    if (*q == 0x0D || *q == 0x0A)
      last = true;
    *q = 0;
    v[i++] = atoi(p);
    if (last || i == N)
      break;
    p = q + 1;
  }
  return i;
}
void read_cr() { fgets(_buf, 256, stdin); }

void horizontal(vector<int> &v) {
  int L = v.size();
  for (int i = 0; i < L; ++i) {
    printf("%d%c", v[i], (i == L - 1) ? '\\n' : ' ');
  }
}
void horizontall(vector<long long> &v) {
  int L = v.size();
  for (int i = 0; i < L; ++i) {
    printf("%lld%c", v[i], (i == L - 1) ? '\\n' : ' ');
  }
}

ll fact[2222223], ifact[2222223];

ll nCk(int n, int k) { return MUL(fact[n], MUL(ifact[n - k], ifact[k])); }

ll solve(int K, string &s) {
  int oof_len = s.size();

  ll ans = 0;
  for (int r = 0; r <= K; ++r) {
    ll m25 = POW(25, r), m26 = POW(26, K - r), mag = MUL(m25, m26);

    ll c = nCk(oof_len + r - 1, oof_len - 1);
    ll local = MUL(c, mag);

    ans = ADD(ans, local);
  }
  return ans;
}

int main() {
  fact[0] = fact[1] = 1;
  ifact[0] = ifact[1] = 1;
  for (int n = 2; n <= 2222222; ++n)
    fact[n] = MUL(fact[n - 1], n);
  ifact[2222222] = INV(fact[2222222]);
  for (int n = 2222222; n > 1; --n)
    ifact[n - 1] = MUL(ifact[n], n);

  int K;
  cin >> K;
  string S;
  cin >> S;
  cout << solve(K, S) << endl;
  return 0;
}


Error: 0

Fixed submission:

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

#define NDEBUG
#include <cassert>

typedef long long ll;
typedef long double Double;
typedef unsigned long long ull;
typedef pair<int, int> ii;
typedef pair<ll, ll> llll;
typedef pair<double, double> dd;

typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<ll> vll;
typedef vector<vector<ll>> vvll;
typedef vector<llll> vllll;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<long double> vD;

#define sz(a) int((a).size())
#define pb push_back
#define eb emplace_back
#define FOR(var, from, to) for (int var = (from); var <= (to); ++var)
#define rep(var, n) for (int var = 0; var < (n); ++var)
#define rep1(var, n) for (int var = 1; var <= (n); ++var)
#define repC2(vari, varj, n)                                                   \\
  for (int vari = 0; vari < (n)-1; ++vari)                                     \\
    for (int varj = vari + 1; varj < (n); ++varj)
#define repC3(vari, varj, vark, n)                                             \\
  for (int vari = 0; vari < (n)-2; ++vari)                                     \\
    for (int varj = vari + 1; varj < (n)-1; ++varj)                            \\
      for (int vark = varj + 1; vark < (n); ++vark)
#define ALL(c) (c).begin(), (c).end()
#define RALL(c) (c).rbegin(), (c).rend()
#define tr(i, c) for (auto i = (c).begin(); i != (c).end(); ++i)
#define found(s, e) ((s).find(e) != (s).end())
#define mset(arr, val) memset(arr, val, sizeof(arr))
#define mid(x, y) ((x) + ((y) - (x)) / 2)
#define IN(x, a, b) ((a) <= (x) && (x) <= (b))
#define cons make_pair
#define clamp(v, lo, hi) min(max(v, lo), hi)
#define ABS(x) max((x), -(x))
#define PQ(T) priority_queue<T, vector<T>, greater<T>>

template <typename T1, typename T2> inline void amin(T1 &a, T2 const &b) {
  if (a > b)
    a = b;
}
template <typename T1, typename T2> inline void amax(T1 &a, T2 const &b) {
  if (a < b)
    a = b;
}
template <typename X, typename T> auto vectors(X x, T a) {
  return vector<T>(x, a);
}
template <typename X, typename Y, typename Z, typename... Zs>
auto vectors(X x, Y y, Z z, Zs... zs) {
  auto cont = vectors(y, z, zs...);
  return vector<decltype(cont)>(x, cont);
}

inline ll square(ll x) { return x * x; }
inline ll gcd(ll a, ll b) {
  while (a)
    swap(a, b %= a);
  return b;
}
inline ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }
template <typename T> inline T mod(T a, T b) { return ((a % b) + b) % b; }

template <typename T> int find_left(vector<T> &v, T elem) {
  return (int)(upper_bound(v.begin(), v.end(), elem) - v.begin()) - 1;
}
template <typename T> int find_right(vector<T> &v, T elem) {
  return (int)(lower_bound(v.begin(), v.end(), elem) - v.begin());
}

const ll MOD = 1000000007LL;

inline ll ADD(ll x, ll y) { return (x + y) % MOD; }
inline ll SUB(ll x, ll y) { return (x - y + MOD) % MOD; }
inline ll MUL(ll x, ll y) { return x * y % MOD; }
inline ll POW(ll x, ll e) {
  ll v = 1;
  for (; e; x = MUL(x, x), e >>= 1)
    if (e & 1)
      v = MUL(v, x);
  return v;
}
inline ll INV(ll y) { /*assert(y%MOD!=0);*/
  return POW(y, MOD - 2);
}
inline ll DIV(ll x, ll y) { return MUL(x, INV(y)); }
ll comb(ll n, ll k) {
  ll v = 1;
  for (ll i = 1; i <= k; i++)
    v = DIV(MUL(v, n - i + 1), i);
  return v;
}

#define INTSPACE 12
char _buf[INTSPACE * 1000000 + 3];

int loadint() {
  if (fgets(_buf, INTSPACE + 3, stdin) == NULL)
    return 0;
  return atoi(_buf);
}

int loadvec(vector<int> &v, int N = -1) {
  if (N == 0) {
    v.clear();
    return 0;
  }
  if (N == -1) {
    N = loadint();
    if (N == 0)
      return 0;
  }
  int bufsize = INTSPACE * N + 3;
  if (fgets(_buf, bufsize, stdin) == NULL)
    return 0;
  v.resize(N);

  int i = 0;
  bool last = false;
  for (char *p = &_buf[0];;) {
    char *q = p;
    while (*q > ' ')
      ++q;
    if (*q == 0x0D || *q == 0x0A)
      last = true;
    *q = 0;
    v[i++] = atoi(p);
    if (last || i == N)
      break;
    p = q + 1;
  }
  return i;
}
void read_cr() { fgets(_buf, 256, stdin); }

void horizontal(vector<int> &v) {
  int L = v.size();
  for (int i = 0; i < L; ++i) {
    printf("%d%c", v[i], (i == L - 1) ? '\\n' : ' ');
  }
}
void horizontall(vector<long long> &v) {
  int L = v.size();
  for (int i = 0; i < L; ++i) {
    printf("%lld%c", v[i], (i == L - 1) ? '\\n' : ' ');
  }
}

ll fact[222223], ifact[222223];

ll nCk(int n, int k) { return MUL(fact[n], MUL(ifact[n - k], ifact[k])); }

ll solve(int K, string &s) {
  int oof_len = s.size();

  ll ans = 0;
  for (int r = 0; r <= K; ++r) {
    ll m25 = POW(25, r), m26 = POW(26, K - r), mag = MUL(m25, m26);

    ll c = nCk(oof_len + r - 1, oof_len - 1);
    ll local = MUL(c, mag);

    ans = ADD(ans, local);
  }
  return ans;
}

int main() {
  fact[0] = fact[1] = 1;
  ifact[0] = ifact[1] = 1;
  for (int n = 2; n <= 222222; ++n)
    fact[n] = MUL(fact[n - 1], n);
  ifact[222222] = INV(fact[222222]);
  for (int n = 222222; n > 1; --n)
    ifact[n - 1] = MUL(ifact[n], n);

  int K;
  cin >> K;
  string S;
  cin >> S;
  cout << solve(K, S) << endl;
  return 0;
}