Submission #44049

#	Time	Username	Problem	Language	Result	Execution time	Memory
44049		wxh010910	Asceticism (JOI18_asceticism)	C++17	100 / 100	14 ms	1408 KiB

asceticism

#include <bits/stdc++.h>

using namespace std;

#define X first
#define Y second
#define mp make_pair
#define pb push_back
#define Debug(...) fprintf(stderr, __VA_ARGS__)

typedef long long LL;
typedef long double LD;
typedef unsigned int uint;
typedef pair <int, int> pii;
typedef unsigned long long uLL;

template <typename T> inline void Read(T &x) {
  char c = getchar();
  bool f = false;
  for (x = 0; !isdigit(c); c = getchar()) {
    if (c == '-') {
      f = true;
    }
  }
  for (; isdigit(c); c = getchar()) {
    x = x * 10 + c - '0';
  }
  if (f) {
    x = -x;
  }
}

template <typename T> inline bool CheckMax(T &a, const T &b) {
  return a < b ? a = b, true : false;
}

template <typename T> inline bool CheckMin(T &a, const T &b) {
  return a > b ? a = b, true : false;
}

const int N = 100005;
const int mod = 1e9 + 7;

int n, m, ans, fac[N], inv[N];

inline int Qow(int x, int y) {
  int r = 1;
  for (; y; y >>= 1, x = 1LL * x * x % mod) {
    if (y & 1) {
      r = 1LL * r * x % mod;
    }
  }
  return r;
}

inline int C(int x, int y) {
  return 1LL * fac[x] * inv[y] % mod * inv[x - y] % mod;
}

int main() {
#ifdef wxh010910
  freopen("d.in", "r", stdin);
#endif
  Read(n), Read(m), fac[0] = fac[1] = inv[0] = inv[1] = 1;
  for (int i = 2; i <= n + 1; ++i) {
    fac[i] = 1LL * fac[i - 1] * i % mod;
    inv[i] = 1LL * (mod - mod / i) * inv[mod % i] % mod;
  }
  for (int i = 2; i <= n + 1; ++i) {
    inv[i] = 1LL * inv[i - 1] * inv[i] % mod;
  }
  for (int i = 0; i <= m; ++i) {
    if (i & 1) {
      ans = (ans - 1LL * C(n + 1, i) * Qow(m - i, n) % mod + mod) % mod;
    } else {
      ans = (1LL * C(n + 1, i) * Qow(m - i, n) + ans) % mod;
    }
  }
  printf("%d\n", ans);
#ifdef wxh010910
  Debug("My Time: %.3lfms\n", (double)clock() / CLOCKS_PER_SEC);
#endif
  return 0;
}

• Subtask 1: 4 / 4
• Subtask 2: 20 / 20
• Subtask 3: 25 / 25
• Subtask 4: 51 / 51