FloppyPianno Key Sort

(C) Corné Dorrestijn 2012
Algorithm to sort out white and black keys on a piano.

Desired result:
  02  04  NN  07  09  11  NN  14  16  NN  19
01  03  05  06  08  10  12  13  15  17  18  20

Pseudocode:

X = 0                   ; Total key count
Y = 3                   ; Max keys in the current block of black keys
Z = 0                   ; Black key count in current block
S = FALSE               ; Black/White key switch
A = []                  ; Black keys array
B = []                  ; White keys array

X++                 ; Increase the current key
IF S                    ; If a black key may be placed
    Z++             ; Increase the black key count (of the current block)
    IF Z == Y           ; If that black key count is equal to the max keys in this block
        Y = Y == 3 ? 4 : 3  ; If maximum keys in this block is 3 make it 4 if not make it 3
        Z = 0           ; Reset the black key count
        B.PUSH(X)       ; Push the current key in the WHITE key array
        S = TRUE        ; Set the switch so that a black key may be placed
    ELSE                ; If the black key count is not equal to the max in this block
        A.PUSH(X)       ; Push the current key in the BLACK key array
        S = FALSE       ; Set the switch so that a white key may be placed
ELSE                    ; If a white key may be placed
    B.PUSH(X)           ; Push the current key in the white key array
    S = TRUE            ; Set the switch so that a black key may be placed


Memory after 8 loops:

i = 8
Y = 4
Z = 1
S = FALSE
A = [2, 4, 7]
B = [1, 3, 5, 6, 8]

ECMAScript 3:

var maxBlock = 3;
var currentInBlock = 0;
var blockSwitch = false;
var blackKeyArray = [];
var whiteKeyArray = [];
for(var i = 1; i <= 49; i++)
{
    if(blockSwitch)
    {
        currentInBlock++;
        if(currentInBlock == maxBlock)
        {
            maxBlock = maxBlock == 3 ? 4 : 3;
            currentInBlock = 0;
            whiteKeyArray.push(i);
            blockSwitch = true;
        }
        else
        {
            blackKeyArray.push(i);
            blockSwitch = false;
        }
    }
    else
    {
        whiteKeyArray.push(i);
        blockSwitch = true;
    }
}

Result:

blackKeyArray = [2, 4, 7, 9, 11, 14, 16, 19, 21, 23, 26, 28, 31, 33, 35, 38, 40, 43, 45, 47];
whiteKeyArray = [1, 3, 5, 6, 8, 10, 12, 13, 15, 17, 18, 20, 22, 24, 25, 27, 29, 30, 32, 34, 36, 37, 39, 41, 42, 44, 46, 48, 49];