RRQR Pivot Selection

Problem

Perform one rank-revealing QR pivot selection step: find the column of A with the largest 2-norm and move it to the first column, shifting the columns before it to the right.

If several columns tie, choose the leftmost one. Return the reordered matrix.

Hint

Moving the largest column to the front maximizes the first pivot in magnitude.

Test cases

case 1

in: [[[1,0,3],[0,1,4]]]

expected: [[3,0,1],[4,1,0]]

case 2

in: [[[2,1],[0,0]]]

expected: [[2,1],[0,0]]

case 3

in: [[[1,2],[0,0],[0,0]]]

expected: [[2,1],[0,0],[0,0]]

case 4

in: [[[0,1],[1,0]]]

expected: [[0,1],[1,0]]

Starter codePython

def rrqr_select_column(A):
    # Your code here
    pass

4 test cases · run your code against them in the editor