feat(codeforces): 964)

codeforces/964/f.cc

@@ -0,0 +1,151 @@
+#include <bits/stdc++.h>
+
+// https://codeforces.com/blog/entry/96344
+
+#pragma GCC optimize("O2,unroll-loops")
+#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
+
+using namespace std;
+
+template <typename... Args>
+void dbg(std::string const &str, Args &&...args) {
+  std::cout << std::vformat(str, std::make_format_args(args...));
+}
+
+template <typename T>
+void dbg(T const &t) {
+  std::cout << t;
+}
+
+template <std::ranges::range T>
+void dbgln(T const &t) {
+  if constexpr (std::is_convertible_v<T, char const *>) {
+    std::cout << t << '\n';
+  } else {
+    for (auto const &e : t) {
+      std::cout << e << ' ';
+    }
+    std::cout << '\n';
+  }
+}
+
+void dbgln() {
+  std::cout << '\n';
+}
+
+template <typename... Args>
+void dbgln(std::string const &str, Args &&...args) {
+  dbg(str, std::forward<Args>(args)...);
+  cout << '\n';
+}
+
+template <typename T>
+void dbgln(T const &t) {
+  dbg(t);
+  cout << '\n';
+}
+
+template <typename T>
+constexpr T MIN = std::numeric_limits<T>::min();
+
+template <typename T>
+constexpr T MAX = std::numeric_limits<T>::min();
+
+template <typename T>
+static T sc(auto &&x) {
+  return static_cast<T>(x);
+}
+
+#define ff first
+#define ss second
+#define eb emplace_back
+#define ll long long
+#define ld long double
+#define vec vector
+#define endl '\n'
+
+#define all(x) (x).begin(), (x).end()
+#define rall(x) (r).rbegin(), (x).rend()
+#define sz(x) static_cast<int>((x).size())
+#define FOR(a, b, c) for (int a = (b); a < (c); ++a)
+#define ROF(a, b, c) for (int a = (b); a > (c); --a)
+
+std::random_device rd;
+std::mt19937 gen(rd());
+
+static constexpr int MOD = 1000000007;
+static constexpr int MAX_N = 2 * 100000 + 1;
+
+static vec<ll> fac(MAX_N + 1, 1);
+bitset<MAX_N> seen;
+
+void solve() {
+  int n, k;
+  cin >> n >> k;
+  vec<int> a(n);
+  seen.reset();
+  for (auto &e : a) {
+    cin >> e;
+  }
+  sort(all(a));
+
+  ll ans = 0;
+  dbgln("----------------------");
+  dbgln(a);
+
+  FOR(i, 0, n) {
+    if (a[i] == 0 || seen[a[i]])
+      continue;
+    seen[a[i]] = true;
+    // count <=, >=
+    int lt = distance(a.begin(), lower_bound(all(a), a[i]));
+    int gt = distance(upper_bound(all(a), a[i]), a.end());
+    int eq = n - lt - gt - 1;
+
+    if (lt + eq < k / 2)
+      continue;
+    eq -= max(0, k / 2 - lt);
+    if (gt + eq < k / 2)
+      continue;
+    eq -= max(0, k / 2 - gt);
+
+    dbgln("x={}, lt={}, gt={}, remaining eq={}", a[i], lt, gt, eq);
+    ans = (ans + (max(1, lt) * max(1, gt)) % MOD) % MOD;
+
+    // count =
+    int left = eq;
+    if (lt < k / 2)
+      eq -= k / 2 - lt;
+    if (gt < k / 2)
+      eq -= k / 2 - gt;
+
+    // - max(0, (k / 2 - lt)) - max(0, (k / 2 - gt)) + 1;
+    //   dbgln("with element {}, have {} choices", a[i], left);
+    //   FOR(i, 1, left) {
+    //     ll nci = fac[left] / (fac[i] * fac[left - i]);
+    //     dbgln("n={} choose i={}, nci={}", n, i, nci);
+    //     ans = (ans + nci) % MOD;
+    //   }
+    // }
+
+    dbgln(ans);
+  }
+}
+
+int main() {
+  cin.tie(nullptr)->sync_with_stdio(false);
+
+  fac[0] = 1LL;
+  FOR(i, 1, MAX_N + 1) {
+    fac[i] = i * fac[i - 1];
+  }
+
+  int t = 1;
+  cin >> t;
+
+  while (t--) {
+    solve();
+  }
+
+  return 0;
+}