{ Analytica Model Reverse_halves, encoding="UTF-8" }
SoftwareVersion 6.3.6


{ System Variables with non-default values: }
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Model Reverse_halves
Title: Reverse halves
Description: Start with array A indexed by I, and a split point N that identifies a position along I. The challenge is to reverse the first N elements of A, and separately reverse the remaining elements after the Nth, to get a new array indexed by I.~
~
The solution should work for 1<=N<IndexLength(I). Within this range you are guaranteed that each section has at least 1 element.
Author: Lonnie Chrisman~
Lumina Decision Systems
Date: Fri, Sep 15, 2023 4:38 PM
DiagState: 2,0,0,1264,500,17,10
WindState: 2,798,342,720,350
FontStyle: Arial,15
FileInfo: 0,Model Reverse_halves,2,2,0,0,W:\Training\Challenges\Reverse halves.ana

Index I
Title: I
Definition: 1..10
NodeLocation: 168,72,1
NodeSize: 64,24

Variable N
Title: N
Description: The position
Definition: 4
Check: 1 <= N < IndexLength(I)
NodeLocation: 168,144,1
NodeSize: 64,24
Aliases: FormNode Fo1853591635
{!60005|Att_AttsToShow: Attribute Check}

Variable A
Title: A
Description: Starting data
Definition: 'a'&@I
NodeLocation: 336,72,1
NodeSize: 64,24
ValueState: 2,1334,53,416,303,,MIDM

Objective Desired_result
Title: Desired result
Definition: Table(I)('a4','a3','a2','a1','a10','a9','a8','a7','a6','a5')
NodeLocation: 496,72,1
NodeSize: 64,24

Module Solutions
Title: Solutions
Description: Don't peek until you've tried it yourself. There are many ways to accomplish this, including many that do not appear here.
NodeLocation: 336,144,1
NodeSize: 64,24
DiagState: 2,289,82,1264,720,17,10
WindState: 2,1092,405,720,350

Variable Solution_3
Title: Solution 2
Description: This one reverses the entire array once, and then shifts it left and right (getting 2 intermediates) so that the elements are in their final position along I. The intermediates are Null-padded, so that there is only one element among them that in non-null, so they are easily combined using Max (which ignores Nulls -- the Max of one element is itself).
Definition: LocalIndex shift:=[ IndexLength(I)-N, -N];~
Max(Reverse(A,I)[@I=@I+shift],shift)
NodeLocation: 120,152,1
NodeSize: 64,24
WindState: 2,546,128,720,350
ValueState: 2,1068,28,817,303,,MIDM

Variable Solution_1
Title: Solution 1
Description: This is probably the most intuitive solution. Split the array into two arrays, reverse each individually, then concatenate them back onto the original index.
Definition: LocalIndex I1 := 1..N;~
LocalIndex I2 := N+1..IndexLength(I);~
Concat( Reverse( A[@I=I1], I1 ), Reverse(A[@I=I2], I2), I1, I2, I )
NodeLocation: 120,64,1
NodeSize: 64,24

Close Solutions

Button Read_challenge_descr
Title: Read challenge description
NodeLocation: 672,84,1
NodeSize: 64,36
OnClick: showWindow(Reverse_halves,'Object')

FormNode Fo1853591635
Title: N
Definition: 0
NodeLocation: 160,304,1
NodeSize: 56,16
Original: N

Objective Your_solution
Title: Your solution
Description: Fill in your solution here.
Definition: {Fill in with your solution}
NodeLocation: 496,144,1
NodeSize: 64,24

Close Reverse_halves