Submission #483458

#	Time	Username	Problem	Language	Result	Execution time	Memory
483458		jalsol	Watching (JOI13_watching)	C++17	100 / 100	26 ms	8536 KiB

watching

#ifdef LOCAL
#include "local.h"
#else
#include <bits/stdc++.h>
#define debug(...)
#define DB(...)
#endif

using namespace std;

const bool __initialization = []() {
    cin.tie(nullptr)->sync_with_stdio(false);
#define TASK "empty"
    if (fopen(TASK".inp", "r")) {
        (void)(!freopen(TASK".inp", "r", stdin));
        (void)(!freopen(TASK".out", "w", stdout)); }
    cout << setprecision(12) << fixed;
    return true;
}();

using ll = long long;
using ld = long double;

#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()

#define For(i, l, r) for (int i = (l); i <= (r); ++i)
#define Ford(i, r, l) for (int i = (r); i >= (l); --i)
#define Rep(i, n) For (i, 0, (n) - 1)
#define Repd(i, n) Ford (i, (n) - 1, 0)
#define Fe(...) for (auto __VA_ARGS__)

template <class C> inline int isz(const C& c) { return static_cast<int>(c.size()); }
template <class T> inline bool chmin(T& a, const T& b) { return (a > b) ? a = b, true : false; }
template <class T> inline bool chmax(T& a, const T& b) { return (a < b) ? a = b, true : false; }

constexpr ld eps = 1e-9;
constexpr int inf = 1e9;
constexpr ll linf = 1e18;

// =============================================================================

constexpr int maxn = 2000 + 5;

int n, np, nq;
int a[maxn];

int dp[maxn][maxn];
int nxtp[maxn], nxtq[maxn];

bool check(int width) {
    int ptr = 1;
    For (i, 1, n) {
        while (ptr <= n && a[ptr] < a[i] + width) ++ptr;
        nxtp[i] = --ptr;
    }

    ptr = 1;
    For (i, 1, n) {
        while (ptr <= n && a[ptr] < a[i] + 2 * width) ++ptr;
        nxtq[i] = --ptr;
    }

    For (i, 0, np) {
        For (j, 0, nq) {
            dp[i][j] = 0;

            if (i > 0) {
                chmax(dp[i][j], nxtp[dp[i - 1][j] + 1]);
            }
            if (j > 0) {
                chmax(dp[i][j], nxtq[dp[i][j - 1] + 1]);
            }

            if (dp[i][j] >= n) return true;
        }
    }
    return false;
}

signed main() {
    cin >> n >> np >> nq;
    For (i, 1, n) cin >> a[i];

    if (np + nq >= n) {
        cout << 1 << '\n';
        return 0;
    }

    sort(a + 1, a + n + 1);

    int L = 1, R = inf;
    int ans = -1;

    while (L <= R) {
        int M = (L + R) / 2;
        if (check(M)) {
            ans = M;
            R = M - 1;
        } else {
            L = M + 1;
        }
    }

    assert(ans != -1);
    cout << ans << '\n';
}

• Subtask 1: 50 / 50
• Subtask 2: 50 / 50