Submission #253892

#	Time	Username	Problem	Language	Result	Execution time	Memory
253892		ChrisT	Watching (JOI13_watching)	C++17	100 / 100	213 ms	16248 KiB

watching

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2005;
typedef long long ll;
typedef pair<int,int> pii;
int dp[MAXN][MAXN], a[MAXN],p,q,n;
int findlast (int cur, int w) {
  return max((int)(lower_bound(a+1,a+1+n,cur-w+1)-a-1),0);
}
bool check (int w) {
  memset(dp,0x3f,sizeof dp); memset(dp[0],0,sizeof dp[0]);
  for (int i = 1; i <= n; i++) {
    int lp = findlast(a[i],w), lq = findlast(a[i],w<<1);
    for (int j = 0; j <= p; j++) {
      dp[i][j] = dp[lq][j] + 1;
      if (j) dp[i][j] = min(dp[i][j],dp[lp][j-1]);
    }
  }
  return dp[n][p] <= q;
}
int main() {
  int ans=INT_MAX;
  scanf ("%d %d %d",&n,&p,&q);
  if (p + q >= n) return !printf ("1\n");
  for (int i = 1; i <= n; i++) scanf ("%d",&a[i]);
  sort(a+1,a+1+n);
  for (int low = 1, high = 1e9,mid; low <= high;) {
    if (check(mid = (low + high)>>1)) high = mid-1, ans = mid;
    else low = mid+1;
  }
  printf ("%d\n",ans);
  return 0;
}

Compilation message (stderr)

watching.cpp: In function 'int main()':
watching.cpp:23:9: 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:25:38: 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",&a[i]);
                                ~~~~~~^~~~~~~~~~~~

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