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哦,钱数的算法我也明白了。1+3+5+...+(2n-1) = n^2,钱数的期望正好变成天数的平方的期望,于是就可以用Dx = Ex^2 - E(x^2)来算了。我反应真慢。In Reply To:求天数期望我是看明白了,就是K个几何分布加起来。可是第二个答案没看懂,总钱数和方差有什么关系? Posted by:ImLazy at 2008-09-16 14:36:06 Followed by: Post your reply here: |
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