Submission #661502

#	Time	Username	Problem	Language	Result	Execution time	Memory
661502		sofija6	Watching (JOI13_watching)	C++14	100 / 100	843 ms	63352 KiB

watching

#include <bits/stdc++.h>
#define ll long long
#define MAXN 2010
using namespace std;
ll a[MAXN],n,p,q;
pair<ll,ll> dp[MAXN][MAXN];
ll Last(ll pos)
{
    ll l=1,r=n,mid,ans;
    while (l<=r)
    {
        mid=(l+r)/2;
        if (a[mid]<=pos)
        {
            ans=mid;
            l=mid+1;
        }
        else
            r=mid-1;
    }
    return ans;
}
bool Check(ll w)
{
    for (ll i=0;i<=n+1;i++)
    {
        for (ll j=0;j<=min(n,p);j++)
            dp[i][j]={0,LLONG_MAX};
    }
    dp[1][0]={1,0};
    for (ll i=1;i<=n;i++)
    {
        for (ll j=0;j<=min(n,p);j++)
        {
            if (!dp[i][j].first)
                continue;
            if (j<p)
            {
                ll pos=Last(a[i]+w-1);
                dp[pos+1][j+1].first=1;
                dp[pos+1][j+1].second=min(dp[pos+1][j+1].second,dp[i][j].second);
            }
            if (dp[i][j].second<q)
            {
                ll pos=Last(a[i]+2*w-1);
                dp[pos+1][j].first=1;
                dp[pos+1][j].second=min(dp[pos+1][j].second,dp[i][j].second+1);
            }
        }
    }
    for (ll i=0;i<=p;i++)
    {
        if (dp[n+1][i].first && dp[n+1][i].second<=q)
            return true;
    }
    return false;
}
int main()
{
    ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
    cin >> n >> p >> q;
    for (ll i=1;i<=n;i++)
        cin >> a[i];
    sort(a+1,a+1+n);
    ll l=1,r=1e9,mid,ans;
    while (l<=r)
    {
        mid=(l+r)/2;
        if (Check(mid))
        {
            ans=mid;
            r=mid-1;
        }
        else
            l=mid+1;
    }
    cout << ans;
    return 0;
}

Compilation message (stderr)

watching.cpp: In function 'long long int Last(long long int)':
watching.cpp:21:12: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   21 |     return ans;
      |            ^~~
watching.cpp: In function 'bool Check(long long int)':
watching.cpp:46:23: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   46 |                 dp[pos+1][j].first=1;
      |                    ~~~^~
watching.cpp:40:23: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
   40 |                 dp[pos+1][j+1].first=1;
      |                    ~~~^~

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