Submission #285282

#	Time	Username	Problem	Language	Result	Execution time	Memory
285282		leductoan	Watching (JOI13_watching)	C++14	100 / 100	358 ms	8696 KiB

watching

#include<bits/stdc++.h>
using namespace std;
#define task "watching"
#define lb lower_bound
#define ub upper_bound
#define ALL(v) (v).begin(),(v).end()
#define zs(v) int((v).size())
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define FOR(i,a,b) for(int i=(a),_b=(b);i<=_b;++i)
#define FORD(i,b,a) for(int i=(b),_a=(a);i>=_a;--i)
#define FOR_(i,a,b) for(int i=(a),_b=(b);i<_b;++i)
typedef long double ld;
typedef long long ll;
typedef pair<int,int> pii;
const int d4i[4]={-1, 0, 1, 0}, d4j[4]={0, 1, 0, -1};
const int d8i[8]={-1, -1, 0, 1, 1, 1, 0, -1}, d8j[8]={0, 1, 1, 1, 0, -1, -1, -1};
const ll mod=1000000007; /// 998244353
const int base=311;
const int N=2e3+5;

int n,s,l,dp[N][N];
ll a[N];

int check(int val)
{
    for(int i=0;i<=s;++i)
    {
        for(int j=0;j<=l;++j)
        {
            dp[i][j]=-1;
        }
    }
    dp[0][0]=0;
    for(int i=0;i<=s;++i)
    {
        for(int j=0;j<=l;++j)
        {
            if(dp[i][j]==-1) continue;
            if(dp[i][j]==n) return true;
            int l=dp[i][j]+1, r=n;
            int id=-1;
            while(l<=r)
            {
                int mid=(l+r)>>1;
                if(a[mid]-a[dp[i][j]+1]+1<=val) id=mid, l=mid+1;
                else r=mid-1;
            }
            dp[i+1][j]=max(dp[i+1][j],id);

            l=dp[i][j]+1, r=n;
            id=-1;
            while(l<=r)
            {
                int mid=(l+r)>>1;
                if(a[mid]-a[dp[i][j]+1]+1<=2*val) id=mid, l=mid+1;
                else r=mid-1;
            }
            dp[i][j+1]=max(dp[i][j+1],id);
        }
    }

    return dp[s][l]>=n;
}
void biot()
{
    cin>>n>>s>>l;
    if(s+l>=n)
    {
        cout<<1;
        return;
    }
    for(int i=1;i<=n;++i) cin>>a[i];
    sort(a+1,a+n+1);
    int l=1, r=1e9, ans=0;
//    cout<<check(16)<<endl;
    while(l<=r)
    {
        int mid=(l+r)>>1;
        if(check(mid)) ans=mid,r=mid-1;
        else l=mid+1;
    }
    cout<<ans;
}
int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
    if(fopen(task".inp","r"))
    {
        freopen(task".inp","r",stdin);
        freopen(task".out","w",stdout);
    }
    biot();
}

Compilation message (stderr)

watching.cpp: In function 'int main()':
watching.cpp:92:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   92 |         freopen(task".inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
watching.cpp:93:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
   93 |         freopen(task".out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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