DCP35 - RGB

'''
This problem was asked by Google.
Given an array of strictly the characters 'R', 'G', and 'B', segregate the values of the array so that all the Rs come first,
the Gs come second, and the Bs come last. You can only swap elements of the array.
Do this in linear time and in-place.
For example, given the array ['G', 'B', 'R', 'R', 'B', 'R', 'G'], it should become ['R', 'R', 'R', 'G', 'G', 'B', 'B'].
'''
from random import randrange

def generateRGB(desiredLength):
    result = list()
    for i in range(desiredLength):
        r = randrange(3)
        if r == 0:
            result.append('R')
        elif r == 1:
            result.append('G')
        else:
            result.append('B')
    return result

def sortRGB(rgb):
    # First, I have to sort "R"s, I will use the bubllesort method
    for i in range(len(rgb)-1):
        for j in range(i+1, len(rgb)):
            if rgb[i] != 'R' and rgb[j] == 'R':
                # SWAP
                rgb[i], rgb[j] = rgb[j], rgb[i]
                break
    # Now, all the "R"s are in the beginning of the list
    # Then, I do the same thing for "G"s
    for i in range(len(rgb)-1):
        if rgb[i] == 'R':
            continue
            # If rgb[i] == 'R', the list is sorted until this spot, so I continue
        for j in range(i+1, len(rgb)):
            if rgb[i] != 'G' and rgb[j] == 'G':
                # SWAP
                rgb[i], rgb[j] = rgb[j], rgb[i]
                break
    return rgb

def prettyPrintRGB(desiredLength):
    rgb = generateRGB(desiredLength)
    RGB = rgb.copy()
    result = sortRGB(rgb)
    print(str(desiredLength) + " elements: " + str(RGB) + " ----> " + str(result))

# MAIN FUNCTION
desiredLengths = list(range(5, 11))
for desiredLength in desiredLengths:
    prettyPrintRGB(desiredLength)