Submission #970480

#	Time	Username	Problem	Language	Result	Execution time	Memory
970480		Whisper	Watching (JOI13_watching)	C++17	50 / 100	1086 ms	732 KiB

watching

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

#define int long long
#define FOR(i, a, b) for (int i = a; i <= b; i++)
#define FORD(i, a, b) for (int i = b; i >= a; i --)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define REPD(i, n) for (int i = n - 1; i >= 0; --i)

#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1)

constexpr ll LINF = (1ll << 60);
constexpr int INF = (1ll << 30);
constexpr int Mod = 1e9 + 7;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

void setupIO(){
    #define name "Whisper"
    //Phu Trong from Nguyen Tat Thanh High School for gifted student
    srand(time(NULL));
    cin.tie(nullptr)->sync_with_stdio(false); cout.tie(nullptr);
    //freopen(name".inp", "r", stdin);
    //freopen(name".out", "w", stdout);
    cout << fixed << setprecision(10);
}

template <class X, class Y>
    bool minimize(X &x, const Y &y){
        X eps = 1e-9;
        if (x > y + eps) {x = y; return 1;}
        return 0;
    }

template <class X, class Y>
    bool maximize(X &x, const Y &y){
        X eps = 1e-9;
        if (x + eps < y) {x = y; return 1;}
        return 0;
    }
int nArr, nSmall, nBig;
const int MAX = 2e3 + 5;

int a[MAX];

void Whisper(){
    cin >> nArr >> nSmall >> nBig;
    for (int i = 1; i <= nArr; ++i) cin >> a[i];
    if (nSmall + nBig > nArr) return void(cout << 1);

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


    auto check = [&](int w){
        //dp(i, j) số máy ảnh ảnh lớn tối thiểu cần sử dụng xét đến i
        //và đã sử dụng j máy ảnh nhỏ

        vector<vector<int>> dp(nArr + 1, vector<int>(nSmall + 1, INF));
        dp[0][0] = 0;
        for (int i = 1; i <= nArr; ++i){
            for (int v = 0; v <= nSmall; ++v){
                if(v > 0)
                    minimize(dp[i][v], dp[i - 1][v - 1]);
                minimize(dp[i][v], dp[i - 1][v] + 1);
                for (int p = 0; p < i; ++p){
                    if (a[i] - a[p + 1] + 1 <= w && v > 0)
                        minimize(dp[i][v], dp[p][v - 1]);
                    if (a[i] - a[p + 1] + 1 <= 2 * w)
                        minimize(dp[i][v], dp[p][v] + 1);
                }
            }
        }
        int ans = INF;
        for (int i = 0; i <= nSmall; ++i){
            minimize(ans, dp[nArr][i]);
        }
        return (ans <= nBig);
    };

    int l = 1, r = 1e9;
    int ans = -1;
    while (l <= r){
        int mid = (l + r) >> 1;
        if(check(mid)) r = mid - 1, ans = mid;
        else l = mid + 1;
    }

    cout << ans;
}


signed main(){
    setupIO();
    int Test = 1;
//    cin >> Test;
    for ( int i = 1 ; i <= Test ; i++ ){
        Whisper();
        if (i < Test) cout << '\n';
    }
}

• Subtask 1: 50 / 50
• Subtask 2: 0 / 50