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295概率困难derivationlong

Robust Cycles in a Random Permutation

题目

Let σ\sigma be a uniformly random permutation of {1,2,,n}\{1, 2, \dots, n\}. Find the expected number of cycles in the cycle decomposition of σ\sigma. Express your answer as a familiar function of nn.

Additional robustness twist: before observation, an independent random relabeling of outcome labels is applied. Compute the same target and justify invariance.

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