Submission #1316301

#TimeUsernameProblemLanguageResultExecution timeMemory
1316301chithanhnguyenCryptography (NOI20_crypto)C++20
100 / 100
99 ms7604 KiB
/* Author: Nguyen Chi Thanh - High School for the Gifted - VNU.HCM (i2528) */ #include <bits/stdc++.h> using namespace std; #define int long long #define ull unsigned long long #define ld long double #define pii pair<int, int> #define fi first #define se second #define __builtin_popcount __builtin_popcountll #define all(x) (x).begin(), (x).end() #define BIT(x, i) (((x) >> (i)) & 1) #define MASK(x) ((1ll << (x))) #define debug(a, l, r) for (int _i = (l); _i <= (r); ++_i) cout << (a)[_i] << ' '; cout << '\n'; struct FenwickTree { int n; vector<int> fen; FenwickTree(int _n) : n(_n), fen(n + 5, 0) {}; void update(int idx, int v) { for (int i = idx; i <= n; i += i & -i) fen[i] += v; } int get(int idx) { int sum = 0; for (int i = idx; i; i -= i & -i) sum += fen[i]; return sum; } }; const int MAXN = 3e5 + 5; const int MOD = 1e9 + 7; int n, a[MAXN], fact[MAXN]; void init() { cin >> n; vector<int> vals; for (int i = 1; i <= n; ++i) { cin >> a[i]; vals.push_back(a[i]); } sort(all(vals)); vals.erase(unique(all(vals)), end(vals)); for (int i = 1; i <= n; ++i) a[i] = (int)(lower_bound(all(vals), a[i]) - begin(vals)) + 1; fact[0] = 1; for (int i = 1; i <= n; ++i) fact[i] = (fact[i - 1] * i) % MOD; } void solve() { FenwickTree fen(n + 5); for (int i = 1; i <= n; ++i) fen.update(i, 1); int res = 0; for (int i = 1; i <= n; ++i) { int reidx = fen.get(a[i]); int contrib = (reidx - 1) * fact[n - i] % MOD; res = (res + contrib) % MOD; fen.update(a[i], -1); } cout << (res + 1) % MOD; } signed main() { #ifdef NCTHANH freopen("input.txt", "r", stdin); freopen("output.txt", "w", stdout); #endif ios_base::sync_with_stdio(0); cin.tie(nullptr); cout.tie(nullptr); init(); solve(); return 0; }
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