Submission #30042

#	Time	Username	Problem	Language	Result	Execution time	Memory
30042		samir_droubi	Watching (JOI13_watching)	C++14	100 / 100	613 ms	17744 KiB

watching

#include <bits/stdc++.h>
using namespace std;
int n,p,q;
const int mxn=2005;
int dp[mxn][mxn];
int a[mxn];
int l[mxn];
int l2[mxn];
int calc(int i,int u)
{
    if(dp[i][u] != -1)  return dp[i][u];
    if( u > p )return (1e9);
    if(i == 0 ) return 0;
    int ans = calc( l[i] - 1 , u + 1 );
    ans = min(ans , 1 + calc( l2[i] - 1 , u ) );
    return dp[i][u] = ans;
}
bool check(int w)
{
    memset(dp,-1,sizeof dp);
    l[0] = 1;
    l2[0] = 1;
    for(int i = 1; i <= n ; ++i)
    {
        l[i] = l[i - 1];
        l2[i] = l2[i - 1];
        while(a[i] - a[ l[i] ] + 1 > w) ++l[i];
        while(a[i] - a[ l2[i] ] + 1 > 2*w) ++l2[i];
    }
    return calc( n , 0 ) <= q;
}
void bs()
{
    int l=1;
    int r=(1e9);
    int ans=-1;
    while( l <= r )
    {
        int md = ( l + r ) / 2;
        if( check( md ) )r = md - 1 , ans = md;
        else l = md + 1;
    }
    printf("%d\n",ans);
}
int main()
{
    scanf("%d%d%d",&n,&p,&q);
    for(int i = 1 ; i <= n ; ++i )
        scanf("%d",&a[i]);
    sort( a + 1 , a + n + 1 );
    bs();
    return 0;
}

Compilation message (stderr)

watching.cpp: In function 'int main()':
watching.cpp:47:29: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d",&n,&p,&q);
                             ^
watching.cpp:49:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d",&a[i]);
                          ^

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