Aaron Parecki

Given a list:
 
[a b c d e f g h]
 
and a command to set the order of the following in the list: [d a c g]
 
Assign the items in the initial list a numeric index:
 
[a b c d e f g h]
[1 2 3 4 5 6 7 8]
 
Build a new map with the input items and their existing numeric order:
 
[
  1 => a
  3 => c
  4 => d
  7 => g
]
 
For each item in the input list in the given order, set the value in the map:
 
[
  1 => d
  3 => a
  4 => c
  7 => g
]
 
For each item in the new map, change the value at the corresponding numeric index of the list:
 
[d b a c e f g h]
[1 2 3 4 5 6 7 8]