zcmimi's blog

arrow_back期望共1篇文章

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zc
2019-12-21 19:47:00
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其实下面给出的a数组没什么鸟用

列出方程:

E = \sum_{i=0}^{n-1} \frac 1n \times ( i+ flag \times E)

解方程: E = \sum_{i=0}^{n-1} \frac 1n \times ( i+ flag \times E) \\\\ E = \sum_{i=0}^{n-1} \frac in + (1 - \frac mn)E \\\\ \frac mnE = \frac {\frac 12n(n-1)}n \\\\ E = \frac {n(n-1)}{2m}

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