feat(codeforces): 799

codeforces/799/g.cc

@@ -0,0 +1,73 @@
+#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;
+
+#define prln(...) std::println(__VA_ARGS__)
+#define pr(...) std::print(__VA_ARGS__)
+
+#ifdef LOCAL
+#define dbgln(...) std::println(__VA_ARGS__)
+#define dbg(...) std::print(__VA_ARGS__)
+#else
+#define dbgln(...)
+#define dbg(...)
+#endif
+//  }}}
+
+void solve() {
+  int n, k;
+  cin >> n >> k;
+  vector<int> a(n);
+  for (auto& e : a) {
+    cin >> e;
+  }
+  vector<int> can(n, 0);
+  for (int i = 0; i < n - 1; ++i) {
+    can[i] = a[i] / 2.0 < a[i + 1];
+  }
+  int ans = 0, window = 0;
+  // had <= , not < k - 1, then had it wrong AGAIN
+  // NOTE: sliding window impl bad - just decide on one approach and go with it
+  for (int i = 0; i < n - 1; ++i) {
+    window += can[i];
+    if (i >= k - 1) {
+      if (window == k) {
+        ++ans;
+      }
+      window -= can[i - k + 1];
+    }
+  }
+  // for (int i = 0; i < n - 1; ++i) {
+  //   can[i] = (i ? can[i - 1] : 0) + (a[i] / 2.0 < a[i + 1]);
+  // }
+  // int ans = 0;
+  // for (int i = k - 1; i < n - 1; ++i) {
+  //   // cout << "i: " << i << endl;
+  //   // NOTE: i - k - 1 before (wrong)
+  //   if (can[i] - (i - k >= 0 ? can[i - k] : 0) == k) {
+  //     // cout << "yes\n";
+  //     ++ans;
+  //   }
+  // }
+  cout << ans << '\n';
+}
+
+int main() {  // {{{
+  cin.tie(nullptr)->sync_with_stdio(false);
+  cin.exceptions(cin.failbit);
+
+  int tc = 1;
+  cin >> tc;
+
+  for (int t = 0; t < tc; ++t) {
+    solve();
+  }
+
+  return 0;
+}
+// }}}