Ruby获取2d数组中的对角线元素

puts (0..2).collect { |i| array[i][i] }

最好是使用矩阵库的一行程序:

require 'matrix'
Matrix.rows(array).each(:diagonal).to_a

基于 Get all the diagonals in a matrix/list of lists in Python

这是为了得到所有的对角线。无论如何,我们的想法是从不同的侧面填充数组,以便对角线在行和列中对齐:

arr = [[1, 2, 3, 4], [3, 4, 5, 6], [5, 6, 7, 8], [2, 3, 4, 5]]

# pad every row from down all the way up, incrementing the padding. 
# so: go through every row, add the corresponding padding it should have.
# then, grab every column, that’s the end result.

padding = arr.size - 1
padded_matrix = []

arr.each do |row|
    inverse_padding = arr.size - padding
    padded_matrix << ([nil] * inverse_padding) + row + ([nil] * padding)
    padding -= 1    
end

padded_matrix.transpose.map(&:compact)

我正在接受@Shai的答案,并提议让它更实用。

arr = [[1, 2, 3, 4], [3, 4, 5, 6], [5, 6, 7, 8], [2, 3, 4, 5]]

padding = [*0..(arr.length - 1)].map { |i| [nil] * i }
=> [[], [nil], [nil, nil], [nil, nil, nil]]

填充还是第二个取决于你想向下还是向上

padded = padding.reverse.zip(arr).zip(padding).map(&:flatten)
=> [[nil, nil, nil, 1, 2, 3, 4], [nil, nil, 3, 4, 5, 6, nil], [nil, 5, 6, 7, 8, nil, nil], [2, 3, 4, 5, nil, nil, nil]]

padded.transpose.map(&:compact)
=> [[2], [5, 3], [3, 6, 4], [1, 4, 7, 5], [2, 5, 8], [3, 6], [4]]