Submission #945975

---

Source Code Expand

#ifdef DEBUG
#define _GLIBCXX_DEBUG
#endif

#include <bits/stdc++.h>

using namespace std;

mt19937 mrand(random_device{} ()); 

int rnd(int x) {
  return mrand() % x;
}

typedef long double ld;
typedef long long ll;

#ifdef DEBUG
#define eprintf(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
#else
#define eprintf(...) ;
#endif

#define pb push_back
#define mp make_pair
#define sz(x) ((int) (x).size())
#define TASK "text"

const int inf = (int) 1.01e9;
const ld eps = 1e-9;
const ld pi = acos((ld) -1.0);

const int mod = (int) 1e9 + 7;

int mult(int x, int y) {
  return (long long) x * y % mod;
}

void add(int &x, int y) {
  if ((x += y) >= mod) {
    x -= mod;
  }
}

const int maxn = 510000;
struct Tree {
  int a[maxn];
  int n;

  void build(int _n) {
    n = _n;
    for (int i = 0; i < n; ++i) {
      a[i] = 0;
    }
  }

  void add(int x, int toadd) {
    for (; x < n; x |= (x + 1)) {
      a[x] += toadd;
    }
  }

  int get(int x) {
    int res = 0;
    for (; x >= 0; x = (x & (x + 1)) - 1) {
      res += a[x];
    }
    return res;
  }
} tree1;

int fact[maxn];

void precalc() {
  fact[0] = 1;
  for (int i = 1; i < maxn; ++i) {
    fact[i] = mult(fact[i - 1], i);
  }
}

int a[maxn];

int n;

int read() {
  if (scanf("%d", &n) < 1) {
    return 0;
  }
  for (int i = 0; i < n; ++i) {
    scanf("%d", a + i);
    --a[i];
  }
  return 1;
}

int used[maxn];

int cnt[maxn];

void solve() {
  memset(used, 0, sizeof(used));

  int zero = 0;
  for (int i = 0; i < n; ++i) {
    if (a[i] >= 0) {
      used[a[i]] = 1;
    } else {
      ++zero;
    }
  }
  cnt[0] = 0;
  for (int i = 0; i < n; ++i) {
    cnt[i + 1] = cnt[i] + !used[i];
  }


  tree1.build(n);

  int res = 0;
  int zerobef = 0;
  long long total = 0;

  for (int i = n - 1; i >= 0; --i) {
    int cur = 0;
    if (a[i] >= 0) {
      add(cur, mult(fact[zero], tree1.get(a[i] - 1)));
      if (zero) {
        add(cur, mult(zerobef, mult(cnt[a[i]], fact[zero - 1])));
      }
      tree1.add(a[i], 1);
      total += zero - cnt[a[i]];
    } else {
      if (zero) {
        add(cur, mult(fact[zero - 1], total % mod));
      }
      if (zero >= 2) {
        add(cur, mult(mult(zerobef, fact[zero - 2]), (long long) zero * (zero - 1) / 2 % mod));
      }
      ++zerobef;
    }
    //eprintf("cur = %d\n", cur);

    add(res, mult(cur, fact[n - i - 1]));
  }
  add(res, fact[zero]);
  printf("%d\n", res);
}

int main() {
  precalc();
#ifdef LOCAL
  freopen(TASK ".out", "w", stdout);
  assert(freopen(TASK ".in", "r", stdin));
#endif

  while (1) {
    if (!read()) {
      break;
    }
    solve();
#ifdef DEBUG
    eprintf("Time %.2f\n", (double) clock() / CLOCKS_PER_SEC);
#endif
  }
  return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int read()’:
./Main.cpp:90:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", a + i);
                       ^

Judge Result