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????????????????????????????????????????? n ????????? S???????????????????????????????
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n ? S????????????????n ??????????????????????????????????
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0.0000
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[ s = \sqrt{\frac{1}{n} \sum_{i=1}^{n} \left(b_i - \frac{1}{n} \sum_{i=1}^{n} b_i \right)^2} ]
???( s ) ?????( b_i ) ?????????( n ) ?????????
???????????????????????????????????????????????????????????????
cur_avg??? cur_avg ?????????????????????????????????????????????
#includeusing namespace std;typedef long long LL;int n;LL S;double ans = 0.0;double avg = 1.0 * S / n;LL *a = new LL[n];void work() { scanf("%d %lld", &n, &S); ans = 0.0; avg = 1.0 * S / n; LL *a = new LL[n]; for (int i = 0; i < n; ++i) { scanf("%lld", &a[i]); } // ????? double sum = 0.0; for (int i = 0; i < n; ++i) { double diff = a[i] - avg; sum += diff * diff; } ans = sqrt(sum / n); printf("%.4f", ans);}
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0.0000
???????????????????? 0.0000?
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