1043

codeforces/1043/d.cc

@@ -0,0 +1,116 @@
+#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;
+
+using i32 = int32_t;
+using u32 = uint32_t;
+using i64 = int64_t;
+using u64 = uint64_t;
+using f64 = double;
+using f128 = long double;
+
+#if __cplusplus >= 202002L
+template <typename T>
+constexpr T MIN = std::numeric_limits<T>::min();
+
+template <typename T>
+constexpr T MAX = std::numeric_limits<T>::max();
+
+template <typename T>
+[[nodiscard]] static T sc(auto&& x) {
+  return static_cast<T>(x);
+}
+
+template <typename T>
+[[nodiscard]] static T sz(auto&& x) {
+  return static_cast<T>(x.size());
+}
+#endif
+
+static void NO() {
+  std::cout << "NO\n";
+}
+
+static void YES() {
+  std::cout << "YES\n";
+}
+
+template <typename T>
+using vec = std::vector<T>;
+
+#define all(x) (x).begin(), (x).end()
+#define rall(x) (x).rbegin(), (x).rend()
+#define ff first
+#define ss second
+
+#ifdef LOCAL
+#define db(...) std::print(__VA_ARGS__)
+#define dbln(...) std::println(__VA_ARGS__)
+#else
+#define db(...)
+#define dbln(...)
+#endif
+//  }}}
+
+const int MAXD = 18;
+u64 POW10[MAXD], PREF[MAXD];
+
+u64 digit_prefix_sum(u64 n) {
+  if (n < 10)
+    return n * (n + 1) / 2;
+  int d = 0;
+  while (POW10[d + 1] <= n)
+    ++d;
+  u64 p = POW10[d];
+  u64 msd = n / p;
+  u64 rest = n % p;
+  return msd * PREF[d] + (msd * (msd - 1) / 2) * p + msd * (rest + 1) +
+         digit_prefix_sum(rest);
+}
+
+void solve() {
+  u64 k;
+  cin >> k;
+  u64 K = k, D = 1;
+  for (u32 i = 0; i < 15; ++i) {
+    u64 base_count = (POW10[i + 1] - POW10[i]) * (i + 1);
+    if (base_count > K) {
+      D = i + 1;
+      break;
+    }
+    K -= base_count;
+  }
+  u64 ans = 0;
+  u64 x = POW10[D - 1] + K / D - 1;
+  if (K % D) {
+    u64 next = x + 1;
+    for (u32 i = 0; i < D - (K % D); ++i)
+      next /= 10;
+    while (next) {
+      ans += next % 10;
+      next /= 10;
+    }
+  }
+  ans += digit_prefix_sum(x);
+  cout << ans << "\n";
+}
+
+int main() {  // {{{
+  cin.tie(nullptr)->sync_with_stdio(false);
+  cin.exceptions(cin.failbit);
+
+  u32 tc = 1;
+  cin >> tc;
+
+  for (u32 t = 0; t < tc; ++t) {
+    solve();
+  }
+
+  return 0;
+}
+// }}}