135 lines
2.3 KiB
C++
135 lines
2.3 KiB
C++
#include <bits/stdc++.h> // {{{
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// https://codeforces.com/blog/entry/96344
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#pragma GCC optimize("O2,unroll-loops")
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#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
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using namespace std;
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template <typename T>
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constexpr T MIN = std::numeric_limits<T>::min();
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template <typename T>
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constexpr T MAX = std::numeric_limits<T>::max();
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template <typename T>
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[[nodiscard]] static T sc(auto&& x) {
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return static_cast<T>(x);
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}
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template <typename T>
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[[nodiscard]] static T sz(auto&& x) {
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return static_cast<T>(x.size());
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}
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using ll = long long;
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using ld = long double;
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template <typename T>
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using vec = std::vector<T>;
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template <typename T, size_t N>
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using arr = std::array<T, N>;
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#define ff first
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#define ss second
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#define eb emplace_back
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#define pb push_back
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#define all(x) (x).begin(), (x).end()
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#define rall(x) (x).rbegin(), (x).rend()
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// }}}
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void solve() {
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string line;
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while (getline(cin, line)) {
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istringstream iss(line);
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ll m, n;
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iss >> m >> n;
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ll x;
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vector<ll> tires;
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vector<bool> has(m + 1, false);
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while (n--) {
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iss >> x;
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tires.push_back(x);
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has[x] = true;
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}
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ll ans = 0;
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ll i = 0;
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while (i < tires.size()) {
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while (i < tires.size() && !has[tires[i]]) {
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i++;
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}
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if (i >= tires.size()) {
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break;
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}
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if (i == tires.size() - 1) {
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++ans;
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break;
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}
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ll best_count = 0;
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ll best_delta = 0;
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for (int advance = i + 1; advance < tires.size(); ++advance) {
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ll count = 0;
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ll delta = tires[advance] - tires[i];
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ll cur = tires[i];
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bool bad = false;
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while (cur <= m - 1) {
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if (has[cur]) {
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++count;
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} else {
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bad = true;
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break;
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}
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cur += delta;
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}
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if (bad) {
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continue;
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}
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if (count > best_count) {
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best_count = count;
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best_delta = delta;
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}
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}
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if (best_delta == 0) {
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has[tires[i]] = false;
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++ans;
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continue;
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}
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ll cur = tires[i];
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while (cur <= m - 1) {
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has[cur] = false;
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cur += best_delta;
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}
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++ans;
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}
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cout << ans << endl;
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}
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}
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int main() { // {{{
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cin.tie(nullptr)->sync_with_stdio(false);
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int t = 1;
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// cin >> t;
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while (t--) {
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solve();
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}
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return 0;
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}
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// }}}
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