红宝石 |数组重复排列（）函数
Array#repeated_permutation() ：repeated_permutation()是一个 Array 类方法，它返回数组元素的所有长度为 n 的重复排列，然后返回数组本身。
Syntax: Array.repeated_permutation()
Parameter: Array
Return: all repeated permutations of length n of the elements of the array, then return the array itself.
示例 #1：
# Ruby code for repeated_permutation() method
# declaring array
a = [18, 22, 33, nil, 5, 6]
# declaring array
b = [1, 4, 1, 1, 88, 9]
# declaring array
c = []
# repeated_permutation method example
puts "repeated_permutation() method form :
#{a.repeated_permutation(2).to_a}\n\n"
puts "repeated_permutation() method form :
#{b.repeated_permutation(1).to_a}\n\n"
puts "repeated_permutation() method form :
#{c.repeated_permutation(4).to_a}\n\n"
输出 ：
repeated_permutation() method form :
[[18, 18], [18, 22], [18, 33], [18, nil], [18, 5], [18, 6], [22, 18], [22, 22], [22, 33], [22, nil], [22, 5], [22, 6], [33, 18], [33, 22], [33, 33], [33, nil], [33, 5], [33, 6], [nil, 18], [nil, 22], [nil, 33], [nil, nil], [nil, 5], [nil, 6], [5, 18], [5, 22], [5, 33], [5, nil], [5, 5], [5, 6], [6, 18], [6, 22], [6, 33], [6, nil], [6, 5], [6, 6]]
repeated_permutation() method form :
[[1], [4], [1], [1], [88], [9]]
repeated_permutation() method form :
[]
示例 #2：
# Ruby code for repeated_permutation() method
# declaring array
a = ["abc", "nil", "dog"]
# declaring array
c = [nil]
# declaring array
b = ["cow", nil, "dog"]
# repeated_permutation method example
puts "repeated_permutation() method form :
#{a.repeated_permutation(2).to_a}\n\n"
puts "repeated_permutation() method form :
#{b.repeated_permutation(1).to_a}\n\n"
puts "repeated_permutation() method form :
#{c.repeated_permutation(4).to_a}\n\n"
输出 ：
repeated_permutation() method form :
[["abc", "abc"], ["abc", "nil"], ["abc", "dog"], ["nil", "abc"], ["nil", "nil"], ["nil", "dog"], ["dog", "abc"], ["dog", "nil"], ["dog", "dog"]]
repeated_permutation() method form :
[["cow"], [nil], ["dog"]]
repeated_permutation() method form :
[[nil, nil, nil, nil]]