feat: 806

codeforces/806/f.cc

@@ -0,0 +1,105 @@
+#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
+//  }}}
+
+void solve() {
+  u32 n;
+  cin >> n;
+
+  vec<u64> a(n);
+  for (auto& e : a)
+    cin >> e;
+
+  vec<u64> pref(n + 1, 0);
+  for (u32 i = 1; i <= n; ++i) {
+    pref[i] = pref[i - 1] + (a[i - 1] < i ? 1 : 0);
+  }
+
+  u64 ans = 0;
+  for (u32 j = 1; j <= n; ++j) {
+    if (a[j - 1] < j) {
+      u64 aj = a[j - 1];
+      u32 limit = aj == 0 ? 0 : (aj - 1 > n ? n : aj - 1);
+      ans += pref[limit];
+    }
+  }
+
+  println("{}", ans);
+}
+
+int main() {  // {{{
+  std::cin.exceptions(std::cin.failbit);
+
+#ifdef LOCAL
+  std::cerr.rdbuf(std::cout.rdbuf());
+  std::cout.setf(std::ios::unitbuf);
+  std::cerr.setf(std::ios::unitbuf);
+#else
+  std::cin.tie(nullptr)->sync_with_stdio(false);
+#endif
+
+  u32 tc = 1;
+  std::cin >> tc;
+
+  for (u32 t = 0; t < tc; ++t) {
+    solve();
+  }
+
+  return 0;
+}
+// }}}