Submission #768424

#	Time	Username	Problem	Language	Result	Execution time	Memory
768424		fanwen	Watching (JOI13_watching)	C++17	100 / 100	24 ms	8668 KiB

watching

/**
 *      author : pham van sam 
 *      created : 28 June 2023 (Wednesday)
 **/

#include <bits/stdc++.h>

using namespace std;
using namespace chrono;

#define MASK(x) (1LL << (x))
#define BIT(x, i) (((x) >> (i)) & 1)
#define ALL(x) (x).begin(), (x).end()
#define REP(i, n) for (int i = 0, _n = n; i < _n; ++i)
#define FOR(i, a, b) for (int i = (a), _b = (b); i <= _b; ++i)
#define FORD(i, a, b) for (int i = (a), _b = (b); i >= _b; --i)
#define FORE(it, s) for (__typeof(s.begin()) it = (s).begin(); it != (s).end(); ++it)

template <typename U, typename V> bool maximize(U &A, const V &B) { return (A < B) ? (A = B, true) : false; }
template <typename U, typename V> bool minimize(U &A, const V &B) { return (A > B) ? (A = B, true) : false; }

const int MAXN = 2e3 + 5;

int N, P, Q, a[MAXN];
int dp[MAXN][MAXN], nxt1[MAXN], nxt2[MAXN];

bool check(int w) {
    FOR(i, 0, P) FOR(j, 0, Q) dp[i][j] = 0;
    FOR(i, 1, N) {
        nxt1[i] = upper_bound(a + 1, a + N + 1, a[i] + w - 1) - a;
        nxt2[i] = upper_bound(a + 1, a + N + 1, a[i] + 2 * w - 1) - a;
    }
    dp[0][0] = 1;
    FOR(i, 0, P) FOR(j, 0, Q) {
        maximize(dp[i + 1][j], nxt1[dp[i][j]]);
        maximize(dp[i][j + 1], nxt2[dp[i][j]]);
        if(dp[i][j] > N) return true;
    }
    return false;
}

void process(void) {
    cin >> N >> P >> Q;
    if(N <= P + Q) return void(cout << 1);
    FOR(i, 1, N) cin >> a[i];
    sort(a + 1, a + N + 1); 
    int l = 0, r = 1e9 + 1;
    while(r - l > 1) {
        int mid = (l + r) >> 1;
        if(check(mid)) r = mid;
        else l = mid;
    }
    cout << r << '\n';
}

signed main() {

    #define TASK "watching"
    if(fopen(TASK".inp", "r")) {
        freopen(TASK".inp", "r", stdin);
        freopen(TASK".out", "w", stdout);
    }

    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    auto start_time = steady_clock::now();
    int test = 1;
    // cin >> test;
    for (int i = 1; i <= test; ++i) {
        process();
        // cout << '\n';
    }

    auto end_time = steady_clock::now();

    cerr << "\nExecution time : " << duration_cast<milliseconds> (end_time - start_time).count() << "[ms]" << endl;

    return (0 ^ 0);
}

Compilation message (stderr)

watching.cpp: In function 'int main()':
watching.cpp:60:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   60 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
watching.cpp:61:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   61 |         freopen(TASK".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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