从n个不同元素中任取m（m≤n）个元素，按照一定的顺序排列起来，叫做从n个不同元素中取出m个元素的一个排列。当m＝n时所有的排列情况叫全排列。-N elements from any different from m (m ≤ n) elements, in accordance with certain order, and called from the n different elements out of m elements of a array. When m = n when th