Submission #950054

#TimeUsernameProblemLanguageResultExecution timeMemory
950054vjudge1Planine (COCI21_planine)C++17
0 / 110
2 ms860 KiB
#include <bits/stdc++.h> using namespace std; #define all(x) x.begin(), x.end() #define ar array #define pb push_back #define ln '\n' #define int long long using i64 = long long; template <class F, class _S> bool chmin(F &u, const _S &v){ bool flag = false; if ( u > v ){ u = v; flag |= true; } return flag; } template <class F, class _S> bool chmax(F &u, const _S &v){ bool flag = false; if ( u < v ){ u = v; flag |= true; } return flag; } struct frac{ int a, b; frac(int a = 0, int b = 1) : a(a), b(b) {} bool operator <=(const frac &t){ return a * t.b <= b * t.a; } }; signed main(){ ios_base::sync_with_stdio(false); cin.tie(nullptr); int n, h; cin >> n >> h; vector <int> x(n), y(n); for ( int i = 0; i < n; i++ ){ cin >> x[i] >> y[i]; } auto ok = [&](int i, int j, int k, int s){ return (x[j] - x[i]) * (y[k] - y[i]) * s >= (x[k] - x[i]) * (y[j] - y[i]) * s; }; vector <frac> L(n / 2), R(n / 2); deque <int> dq; dq.pb(0); for ( int i = 1; i + 1 < n; i++ ){ while ( dq.size() > 1 && ok(dq[(int)dq.size() - 2], dq.back(), i, -1) ){ dq.pop_back(); } if ( i % 2 == 0 ){ int j = dq.back(); int a = y[i] - y[j], b = x[i] - x[j]; L[i / 2 - 1] = frac((h - y[j]) * b + a * x[j], a); } dq.pb(i); } dq.clear(); dq.pb(n - 1); for ( int i = n - 2; i > 0; i-- ){ while ( dq.size() > 1 && ok(dq[1], dq[0], i, -1) ){ dq.pop_front(); } if ( i % 2 == 0 ){ int j = dq.front(); int a = y[j] - y[i], b = x[j] - x[i]; R[i / 2 - 1] = frac((h - y[i]) * b + a * x[i], a); } dq.push_front(i); } int ans = 1; frac lst = R[0]; for ( int i = 1; i < n / 2; i++ ){ if ( L[i] <= lst || L[i].b ){ if ( R[i] <= lst && R[i].b ){ lst = R[i]; } } else{ ans++; lst = R[i]; } } cout << ans; cout << '\n'; }
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