Submission #707815

#	Time	Username	Problem	Language	Result	Execution time	Memory
707815		Alihan_8	Watching (JOI13_watching)	C++17	100 / 100	318 ms	31604 KiB

watching

#include <bits/stdc++.h>
// include <ext/pb_ds/assoc_container.hpp>
// include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
using namespace std;
#define all(x) x.begin(), x.end()
#define pb push_back
// define ordered_set tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>
#define mpr make_pair
#define ln '\n'
void IO(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
#define int long long
const int N = 2e3+1;
int dp[N][N];
bool chmin(int &x, int y){
    bool flag = false;
    if ( x > y ){
        x = y; flag |= true;
    }
    return flag;
}
signed main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n, P, Q; cin >> n >> P >> Q;
    chmin(P, n), chmin(Q, n);
    vector <int> p(n);
    for ( auto &i: p ) cin >> i;
    sort(all(p));
    p.resize(unique(all(p))-p.begin());
    n = (int)p.size();
    const int inf = 1e16+1;
    auto ok = [&](int w){
        for ( int i = 0; i <= n; i++ ){
            for ( int j = 0; j <= P; j++ ){
                dp[i][j] = inf;
            }
        }
        for ( int i = 0; i <= P; i++ ) dp[0][i] = 0;
        auto f = [&](int x){
            return lower_bound(all(p), x)-p.begin();
        };
        for ( int i = 1; i <= n; i++ ){
            int L = f(p[i-1]-w*2+1), R = f(p[i-1]-w+1);
            for ( int j = 0; j <= P; j++ ){
                chmin(dp[i][j], dp[L][j]+1);
                if ( j ) chmin(dp[i][j], dp[R][j-1]);
            }
        }
        return dp[n][P] <= Q;
    };
    int l = 1, r = 1e9;
    while ( l < r ){
        int md = (l+r) >> 1;
        if ( ok(md) ) r = md;
        else l = md+1;
    }
    cout << l;

    cout << '\n';
}

Compilation message (stderr)

watching.cpp: In function 'void IO(std::string)':
watching.cpp:11:29: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   11 | void IO(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
      |                      ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
watching.cpp:11:70: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   11 | void IO(string name){freopen((name+".in").c_str(),"r",stdin); freopen((name+".out").c_str(),"w",stdout);}
      |                                                               ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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