Submission #228363

#	Time	Username	Problem	Language	Result	Execution time	Memory
228363		Nayna	Watching (JOI13_watching)	C++14	50 / 100	1094 ms	16000 KiB

watching

#include <bits/stdc++.h>

using namespace std;
const int mxn = 2e3+5;
typedef long long ll;
const ll inf = 1e9+5;
int arr[mxn];
int dp[mxn][mxn];
int n, P, Q;

bool solve(ll w)
{
    for(int i = 0; i <= n; i++)
        for(int r = 0; r <= n; r++) dp[i][r] = inf;
    dp[0][0] = 0;
    for(int i = 1; i <= n; i++)
    {
        for(int r = 0; r <= P; r++)
        {
            int x = upper_bound(arr+1, arr+n+1, arr[i]-w)-arr-1;
            int y = upper_bound(arr+1, arr+n+1, arr[i]-w-w)-arr-1;
            if(r) dp[i][r] = min(dp[i][r], dp[x][r-1]);
            dp[i][r] = min(dp[i][r], dp[y][r]+1);
        }
    }
    for(int i = 0; i <= P; i++)
        if(dp[n][i]<=Q) return true;
    return false;
}
int main()
{

    scanf("%d%d%d", &n, &P, &Q);

    P = min(n, P);
    Q = min(n, Q);

    for(int i = 1; i <= n; i++) scanf("%d", &arr[i]);

    sort(arr+1, arr+n+1);

    int lo = 1, hi = 1e9+5, ans = inf;

    while(lo<=hi)
    {
        int mid = (lo+hi)>>1;
        if(solve(mid))
        {
            hi = mid-1;
            ans = min(ans, mid);
        }
        else lo = mid+1;
    }
    printf("%d\n", ans);
    return 0;
}

Compilation message (stderr)

watching.cpp: In function 'int main()':
watching.cpp:33:10: 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:38:38: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for(int i = 1; i <= n; i++) scanf("%d", &arr[i]);
                                 ~~~~~^~~~~~~~~~~~~~~

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