[理工] [機率]-排列組合

[electrify (小狼狗)]

In how many ways can we give 6 differernt gifts to 4

students and each of them get at least one gift.








           4        3        4            4
ans:4^6-{C  *[3^6-C  *2^6]+C   *[2^6-2]+C   *1}
           3        2        2            1


應該還有別的方式解，不過就是想不出來..

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推 youmehim:4C2 * 6C2 * 4C2 * 2! + 4 * 6C3 * 3!