Submission #365299

#	Time	Username	Problem	Language	Result	Execution time	Memory
365299		Bill_00	Watching (JOI13_watching)	C++14	50 / 100	145 ms	16108 KiB

watching

#include <bits/stdc++.h>
using namespace std;
int a[2001];
int dp[2001][2001];
int pre1[2001],pre2[2001];
int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int n,p,q;
	cin >> n >> p >> q;
	for(int i=1;i<=n;i++){
		cin >> a[i];
	}
	sort(a+1,a+n+1);
	if(p+q>=n){
		cout << 1;
		return 0;
	}
	a[0]=-1000000000;
	int l=1,r=1000000000;
	while(l!=r){
		int mid=l+r>>1;
		int k=0,y=0;
		for(int i=1;i<=p;i++){
			dp[0][i]=0;
		}
		for(int i=1;i<=n;i++){
			dp[i][0]=1e9;
			while((a[i]-mid)>=a[k+1]) k++;
			while((a[i]-2*mid)>=a[y+1]) y++;
			pre1[i]=k;
			pre2[i]=y;
		}
		for(int i=1;i<=n;i++){
			for(int j=1;j<=p;j++){
				int b=a[i]-mid+1;
				int id=pre1[i];
				b=a[i]-2*mid+1;
				int id1=pre2[i];
				dp[i][j]=min(dp[id][j-1],dp[id1][j]+1);
			}
		}
		if(dp[n][p]>q){
			l=mid+1;
		}
		else r=mid;
	}
	//cout << l << endl;
	int mid=l,k=0,y=0;
	for(int i=1;i<=p;i++){
		dp[0][i]=0;
	}
	for(int i=1;i<=n;i++){
		dp[i][0]=1e9;
		while((a[i]-mid)>=a[k+1]) k++;
		while((a[i]-2*mid)>=a[y+1]) y++;
		pre1[i]=k;
		pre2[i]=y;
	}
	for(int i=1;i<=n;i++){
		for(int j=1;j<=p;j++){
			int b=a[i]-mid+1;
			int id=pre1[i];
			b=a[i]-2*mid+1;
			int id1=pre2[i];
			dp[i][j]=min(dp[id][j-1],dp[id1][j]+1);
			//cout << dp[i][j] << ' ' << i << ' ' << j << endl;
		}
	}
	if(dp[n][p]>q){
		l++;
	}
	cout << l;
}

Compilation message (stderr)

watching.cpp: In function 'int main()':
watching.cpp:23:12: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   23 |   int mid=l+r>>1;
      |           ~^~
watching.cpp:37:9: warning: variable 'b' set but not used [-Wunused-but-set-variable]
   37 |     int b=a[i]-mid+1;
      |         ^
watching.cpp:63:8: warning: variable 'b' set but not used [-Wunused-but-set-variable]
   63 |    int b=a[i]-mid+1;
      |        ^

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