玩转前缀和专题：01

import java.math.BigInteger;
import java.util.*;

public class CF470C {
// static int dir[][] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};

public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int k=sc.nextInt();
int a[] = new int[n + 1];
int sum[] = new int[n + 1];
Set set=new TreeSet();
set.clear();
// int k = sc.nextInt();
for (int i = 1; i <= n; i++) {
a[i] = sc.nextInt();
sum[i] = sum[i - 1] + a[i];

}
for(int i=0;i<=(n-k);i++){
int j=i+k;
int tmp=sum[j]-sum[i];
// System.out.println(tmp);
//if(!set.contains(tmp);
if(!set.contains(tmp)) set.add(sum[j]-sum[i]);

}
int ans[]=new int[set.size()];
Object []kk=set.toArray();
Arrays.sort(kk);
System.out.println(kk[0]);
/* for(int i=0;i<kk.length;i++)
System.out.print(kk[i]);
*/
}

}