Submission #1027486

#	Time	Username	Problem	Language	Result	Execution time	Memory
1027486		caterpillow	Feast (NOI19_feast)	C++17	100 / 100	92 ms	12884 KiB

feast

#include <bits/stdc++.h>

using namespace std;

using db = long double;
using ll = long long;
using pl = pair<ll, ll>;
using pi = pair<int, int>;
#define vt vector
#define f first
#define s second
#define pb push_back
#define all(x) x.begin(), x.end() 
#define size(x) ((int) (x).size())
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define ROF(i, a, b) for (int i = (b) - 1; i >= (a); i--)
#define F0R(i, b) FOR (i, 0, b)
#define endl '\n'
const ll INF = 1e18;
const int inf = 1e9;

template<typename Tuple, size_t... Is>
void print_tuple(const Tuple& t, index_sequence<Is...>) {
    ((cerr << (Is == 0 ? "{" : ", ") << get<Is>(t)), ...);
    cerr << "}";
}

template<typename... Args>
ostream& operator<<(ostream& os, const tuple<Args...>& t) {
    print_tuple(t, index_sequence_for<Args...>{});
    return os;
}

ostream& operator<<(ostream& os, string& s) {
    for (char c : s) os << c; 
    return os;
}

template<template<typename> class Container, typename T>
ostream& operator<<(ostream& os, Container<T> o) {
    os << "{"; 
    int g = size(o); 
    for (auto i : o) os << i << ((--g) == 0 ? "" : ", "); 
    os << "}";
    return os;
}

template<typename T, typename V>
ostream& operator<<(ostream& os, const pair<T, V> p) {
    os << "{" << p.f << ", " << p.s << "}";
    return os;
}

template <typename T, typename... V>
void printer(const char *names, T &&head, V &&...tail) {
    int i = 0;
    while (names[i] != '\0' && names[i] != ',') i++;
    constexpr bool is_str = is_same_v<decay_t<T>, const char*>;
    if constexpr (is_str) cerr << head; // ignore directly passed strings
    else cerr.write(names, i) << " = " << head; 
    if constexpr (sizeof...(tail)) cerr << (is_str ? "" : ","), printer(names + i + 1, tail...);
    else cerr << endl;
}

#ifdef LOCAL
#define dbg(...) std::cerr << __LINE__ << ": ", printer(#__VA_ARGS__, __VA_ARGS__)
#else
#define dbg(x...)
#define cerr if (0) std::cerr
#endif

/*

aliens trick

dp[i] = max value of eating first i dishes
dp[i] = min(dp[i - 1], max (j < i) dp[j] + sfx[j + 1] - sfx[i + 1])

*/

ll n, k;
vt<ll> a, sfx;

// tiebreak by minimum # of arrays used
pl check(ll penalty) {
    vt<pl> dp(n + 1);
    ll best = sfx[0], used = 0;
    F0R (i, n) {
        dp[i + 1] = dp[i];
        if (best - sfx[i + 1] - penalty > dp[i + 1].f) {
            dp[i + 1] = {best - sfx[i + 1] - penalty, used + 1};
        } else if (best - sfx[i + 1] - penalty == dp[i + 1].f && used + 1 < dp[i + 1].s) {
            dp[i + 1] = {best - sfx[i + 1] - penalty, used + 1};
        }
        if (dp[i + 1].f + sfx[i + 1] > best) tie(best, used) = dp[i + 1], best += sfx[i + 1];
        else if (dp[i + 1].f + sfx[i + 1] == best && used > dp[i + 1].s) tie(best, used) = dp[i + 1], best += sfx[i + 1];
    }
    return dp[n];
}

main() {
    cin.tie(0)->sync_with_stdio(0);
    
    cin >> n >> k;
    a.resize(n);
    sfx.resize(n + 1);
    F0R (i, n) cin >> a[i];
    copy(all(a), sfx.begin());
    ROF (i, 0, n) sfx[i] += sfx[i + 1];

    // more penalty = fewer arrays
    // want to find smallest penalty such that <= k arrays
    ll lo = -1, hi = 1e12;
    while (hi - lo > 1) {
        ll m = (lo + hi) / 2;
        auto [cost, used] = check(m);
        if (used > k) lo = m;
        else hi = m;
    }
    auto [cost, used] = check(hi);
    ll ans = cost + hi * k;
    cout << ans << endl;
}

Compilation message (stderr)

feast.cpp:101:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
  101 | main() {
      | ^~~~

• Subtask 1: 4 / 4
• Subtask 2: 8 / 8
• Subtask 3: 18 / 18
• Subtask 4: 10 / 10
• Subtask 5: 11 / 11
• Subtask 6: 20 / 20
• Subtask 7: 29 / 29