add back contest

codeforces/826/1741e.cc

@@ -0,0 +1,82 @@
+#include <bits/stdc++.h>  // {{{
+
+#include <version>
+#ifdef __cpp_lib_ranges_enumerate
+#include <ranges>
+namespace rv = std::views;
+namespace rs = std::ranges;
+#endif
+
+#pragma GCC optimize("O2,unroll-loops")
+#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
+
+using namespace std;
+
+using i16 = int16_t;
+using u16 = uint16_t;
+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();
+#endif
+
+#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;
+  vector<i64> a(n);
+  for (auto& e : a) cin >> e;
+
+  vector<bool> dp(n + 1, false);
+  dp[0] = true;
+  for (i32 i = 1; i <= n; ++i) {
+    if (i + a[i - 1] <= n && dp[i - 1]) {
+      dp[i + a[i - 1]] = true;
+    }
+    if (i - a[i - 1] - 1 >= 0 && dp[i - a[i - 1] - 1]) {
+      dp[i] = true;
+    }
+  }
+
+  if (dp.back()) {
+    cout << "YES\n";
+  } else {
+    cout << "NO\n";
+  }
+}
+
+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;
+}
+// }}}
+