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Permutation and Combination


The permutation of n elements is the number of arrangements of these elements such that in no two arrangements, the elements are listed exactly in the same order. If the number of elements of a set is n, then the permutation of these elements is n!.

For example, the permutation of five elements is 5! = 5 × 4 × 3 × 2 × 1 = 120. That is, we can arrange the given five elements in 120 different ways such that no two arrangements are in the same order.