feat: usaco

usaco/bronze/complete-search/tracing.cc

@@ -0,0 +1,168 @@
+#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"; }
+
+#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
+//  }}}
+
+vector<pair<i32, i32>> trace(251);
+
+void solve() {
+  /*
+     - # cows patient 0
+     - k bounds
+
+     1. sort by time to "sim" interactions
+
+    - say x and y shake; unless wek one is sick, wedk consequences
+    (i.e. who gets sick)
+    - only ONE starts out
+
+    - guess ONE cow is patient zero, run sim
+    - guess all k from 0 to 251?, taking min of low bound, max of high bound
+
+    k = 250 -> infinity
+     bsearch <- no (if can achieve state w/ k=i, doesn't mean k=i-1, nor k=i+1)
+
+NOTE: only candidates for patient zero are initial set 0s, since cows stay sick
+     */
+
+  u32 n, t;
+  cin >> n >> t;
+  string state;
+  cin >> state;
+  state = '0' + state;
+
+  u32 t_;
+  for (u32 i = 0; i < t; ++i) {
+    cin >> t_;
+    cin >> trace[t_].ff >> trace[t_].ss;
+    // NOTE: forgot the one-indexin
+  }
+
+  u32 lb = numeric_limits<u32>::max(), ub = 0;
+  u32 count = 0;
+
+  /*
+
+
+     a bunch of cows shake hooves because the gay USACO (usa computing olympiad)
+     just decided to theme everything cows
+
+     and for some K, a cow can only transmit what you have (STDs)
+     after at most K hooveshakes
+
+     but i misread it as saying that if they contract what you have (an STD)
+     they can only transmit the STD up to K days later
+     not after they have sex k times (which is what you do, let k approach
+     infinity)
+
+     ok. then, after that, i missed k=0 basecase
+     then, after that
+     basically, i only counted when someone transmitted an std & infecting someone
+     instead, i should've counted the cow having sex with ANYONE, even if they already 
+     have an std, it still counts as a handshake
+
+     core note: once realize wrong, reexamine entire problem solution (has rpercussions) rather than what u see is wrong
+     */
+
+  for (u32 i = 1; i <= n; ++i) {
+    bool zero = false;
+    for (u32 k = 0; k <= 250; ++k) {
+      vector<u32> shakes(n + 1, 0);
+      string cur_state(n + 1, '0');
+      cur_state[i] = '1';
+
+      for (t_ = 1; t_ <= 250; ++t_) {
+        auto [a, b] = trace[t_];
+        if (a == 0) {
+          continue;
+        }
+
+        if (cur_state[a] == '1') {
+          ++shakes[a];
+        }
+        if (cur_state[b] == '1') {
+          ++shakes[b];
+        }
+        if (cur_state[a] == '0' && cur_state[b] == '1' && shakes[b] <= k) {
+          cur_state[a] = '1';
+        } else if (cur_state[b] == '0' && cur_state[a] == '1' &&
+                   shakes[a] <= k) {
+          cur_state[b] = '1';
+        }
+      }
+
+      if (cur_state == state) {
+        zero = true;
+        lb = min(lb, k);
+        ub = max(ub, k);
+      }
+    }
+    count += zero;
+  }
+
+  cout << count << ' ' << lb << ' ' << (ub == 250 ? "Infinity" : to_string(ub))
+       << '\n';
+}
+
+int main() { // {{{
+  cin.tie(nullptr)->sync_with_stdio(false);
+  cin.exceptions(cin.failbit);
+
+#define PROBLEM_NAME "tracing"
+
+#ifdef LOCAL
+  freopen("io/" PROBLEM_NAME ".in", "r", stdin);
+  freopen("io/" PROBLEM_NAME ".out", "w", stdout);
+#else
+  freopen(PROBLEM_NAME ".in", "r", stdin);
+  freopen(PROBLEM_NAME ".out", "w", stdout);
+#endif
+
+  solve();
+
+  return 0;
+}
+// }}}