Submission #40349

#	Time	Username	Problem	Language	Result	Execution time	Memory
40349		krauch	Watching (JOI13_watching)	C++14	100 / 100	172 ms	9192 KiB

watching

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair < int, int > PII;

#define F first
#define S second
#define mkp make_pair
#define eb emplace_back
#define all(a) a.begin(), a.end()
#define sz(a) (int)a.size()
#define forn(x, a, b) for (int x = a; x <= b; ++x)
#define for1(x, a, b) for (int x = a; x >= b; --x)

const ll ool = 1e18 + 9;
const int N = 3e3 + 3, oo = 1e9 + 9;

int n, P, Q, a[N], d[N][N];

bool check(int W) {
    int ptr = 1;
    forn(i, 0, P) forn(j, 0, Q) d[i][j] = 1;
    forn(i, 0, P) {
        forn(j, 0, Q) {
            if (d[i][j] == -1) continue;
            int ptr = d[i][j];
            while (ptr <= n && a[ptr] - a[d[i][j]] + 1 <= W) {
                ++ptr;
            }
            d[i + 1][j] = max(d[i + 1][j], ptr);
            while (ptr <= n && a[ptr] - a[d[i][j]] + 1 <= 2 * W) {
                ++ptr;
            }
            d[i][j + 1] = max(d[i][j + 1], ptr);
        }
    }
    return (d[P][Q] == n + 1);
}

int main() {

    #ifdef krauch
        freopen("input.txt", "r", stdin);
    #endif

    cin >> n >> P >> Q;
    Q = min(Q, n);
    P = min(P, n - Q);
    forn(i, 1, n) {
        cin >> a[i];
    }

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

    int l = 1, r = a[n];
    while (l < r) {
        int mid = (l + r) >> 1;
        if (check(mid)) r = mid;
        else l = mid + 1;
    }

    cout << l << "\n";

    return 0;
}

Compilation message (stderr)

watching.cpp: In function 'bool check(int)':
watching.cpp:23:9: warning: unused variable 'ptr' [-Wunused-variable]
     int ptr = 1;
         ^

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