48 lines
1.1 KiB
C++
48 lines
1.1 KiB
C++
#include <stdio.h>
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#include <string.h>
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#include <iostream>
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#include <algorithm>
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#include <vector>
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#include <queue>
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#include <set>
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#include <map>
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#include <string>
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#include <math.h>
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#include <stdlib.h>
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#include <time.h>
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using namespace std;
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double x[50010];
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int main()
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{
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int T;
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int n,k;
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scanf("%d",&T);
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while(T--){
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scanf("%d%d",&n,&k);
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for(int i = 0;i < n;i++)
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scanf("%lf",&x[i]);
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sort(x,x+n);
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if(n == k){
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printf("0\n");
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continue;
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}
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int cnt = n-k;
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double sum = 0;
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double sum2 = 0;
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for(int i = 0;i < cnt;i++){
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sum += x[i];
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sum2 += x[i]*x[i];
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}
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double ans = sum2 - 2*sum*(sum/cnt) + cnt*(sum/cnt)*(sum/cnt);
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for(int i = cnt;i < n;i++){
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sum += x[i];
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sum2 += x[i]*x[i];
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sum -= x[i-cnt];
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sum2 -= x[i-cnt]*x[i-cnt];
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ans = min(ans,sum2-2*sum*(sum/cnt)+cnt*(sum/cnt)*(sum/cnt));
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}
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printf("%.10lf\n",ans);
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}
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return 0;
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}
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