Submission #1124203

#	Time	Username	Problem	Language	Result	Execution time	Memory
1124203		seoul_korea	Cryptography (NOI20_crypto)	C++17	100 / 100	120 ms	10008 KiB

Crypto

#include <bits/stdc++.h>

using namespace std;

#define TASK "NOI20_crypto"
#define int long long
#define REP(i, n) for(int i = 1; i <= n; i++)
#define FOR(i, a, b) for(auto i = a; i <= b; i++)
#define FORD(i, a, b) for(auto i = a; i >= b; i--)
template<class T> bool maximize(T& a, T b) { if(a < b) return a = b, 1; return 0; }
template<class T> bool minimize(T& a, T b) { if(a > b) return a = b, 1; return 0; }

const int N = (int)3e5 + 7, MOD = (int)1e9 + 7;
int a[N], fact[N];
int n;

void add(int& a, int b)
{
    a += b;
    if(a >= MOD) a -= MOD;
    if(a < 0) a += MOD;
}

struct FenwickTree
{
    vector<int> BIT;
    FenwickTree(int _sz)
    {
        BIT.assign(_sz + 1, 0);
    }

    void Ins(int x, int val)
    {
        int sz = BIT.size();
        for(; x < sz; x += x & -x) BIT[x] += val;
    }

    int Get(int x)
    {
        int res = 0;
        for(; x > 0; x -= x & -x)
            res += BIT[x];
        return res;
    }
};

signed main()
{
    cin.tie(0)->ios_base::sync_with_stdio(0);

    if(fopen("TASK.INP", "r")) freopen("TASK.INP", "r", stdin);
    if(fopen(TASK".INP", "r")) {
        freopen(TASK".INP", "r", stdin);
        freopen(TASK".OUT", "w", stdout);
    }

    cin >> n;
    FenwickTree tree(n + 10);
    vector<int> zip;
    REP(i, n)
    {
        cin >> a[i];
        zip.push_back(a[i]);
    }

    sort(zip.begin(), zip.end());
    zip.resize(unique(zip.begin(), zip.end()) - zip.begin());
    REP(i, n)
    {
        a[i] = lower_bound(zip.begin(), zip.end(), a[i]) - zip.begin() + 1;
        tree.Ins(a[i], 1);
    }

    fact[0] = 1;
    REP(i, n)
        fact[i] = fact[i - 1] * i % MOD;
    int ans = 0;
    REP(i, n)
    {
        int p = tree.Get(a[i]);
        add(ans, (p - 1) * fact[n - i] % MOD);
        tree.Ins(a[i], -1);
    }
    add(ans, 1);
    cout << ans << endl;
    /*

    *
    x*
    **x
    *x**
    ***xx

    */

    return 0;
}

Compilation message (stderr)

Crypto.cpp: In function 'int main()':
Crypto.cpp:51:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |     if(fopen("TASK.INP", "r")) freopen("TASK.INP", "r", stdin);
      |                                ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Crypto.cpp:53:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   53 |         freopen(TASK".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Crypto.cpp:54:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   54 |         freopen(TASK".OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 9 / 9
• Subtask 3: 10 / 10
• Subtask 4: 11 / 11
• Subtask 5: 21 / 21
• Subtask 6: 13 / 13
• Subtask 7: 19 / 19
• Subtask 8: 12 / 12