DEV Community: Stanley Zheng

pgexercise - members

Stanley Zheng — Mon, 30 Jul 2018 19:34:11 +0000

Been working through postgres exercises; there are some that are straight forward and others with multiple solutions. An example of this is the below.

Find the count of members who have made at least one booking
Question findable here

the more ineffective way to do this. (my first pass)

select count(1) from cd.members 
where memid 
IN (select memid from cd.bookings 
    where slots is not null)

you can group them easier by checking distinct counts and doing the below. ( the distinct is a subquery)

select count(distinct memid) from cd.bookings.

Codefights alphabeticShift

Stanley Zheng — Sun, 22 Jul 2018 22:28:35 +0000

Solutions for this codefight problem solution
https://app.codesignal.com/arcade/intro/level-6/PWLT8GBrv9xXy4Dui/description

Given a string, replace each its character by the next one in the English alphabet (z would be replaced by a).

Example

For inputString = "crazy", the output should be
alphabeticShift(inputString) = "dsbaz".

First Pass with mutuable memory

def alphabeticShift(inputString):

    new_word = []
    for i in inputString:
        current = ord(i)
        print (current)
        current = (current + 1)
        if current > 122:
            current = current - 26

        new_word.append(chr(current))

    return ''.join(new_word)

second pass a bit cleaner using lambdas



def ordshift(i):
    current = ord(i) + 1
    if current > 122:
        current = current - 26
    return chr(current)

def alphabeticShift(inputString):

    new_word = list(map(ordshift, inputString ))
    return ''.join(new_word)

chessBoardColorCalculator

Stanley Zheng — Sun, 22 Jul 2018 21:53:13 +0000

my solution to this code fights problem
https://app.codesignal.com/arcade/intro/level-6/t97bpjfrMDZH8GJhi/description

generates an odd and even offset board and checks their reference values

Given two cells on the standard chess board, determine whether they have the same color or not.

def chessBoardCellColor(cell1, cell2):
    [fooa, foob] = cell1
    [bara, barb] = cell2

    fooa = ord(fooa) % 2 
    foob = int(foob) % 2

    bara = ord(bara) % 2 
    barb = int(barb) % 2

    board = [[(i+1)%2 for i in range(0,9)], [i%2 for i in range(0,9)]]

    return True if board[fooa][foob] == board[bara][barb] else False

chessBoardColorCalculator

Stanley Zheng — Sun, 22 Jul 2018 21:52:51 +0000

my solution to this code fights problem
https://app.codesignal.com/arcade/intro/level-6/t97bpjfrMDZH8GJhi/description

generates an odd and even offset board and checks their reference values

Given two cells on the standard chess board, determine whether they have the same color or not.

`
def chessBoardCellColor(cell1, cell2):
[fooa, foob] = cell1
[bara, barb] = cell2

fooa = ord(fooa) % 2 
foob = int(foob) % 2

bara = ord(bara) % 2 
barb = int(barb) % 2

board = [[(i+1)%2 for i in range(0,9)], [i%2 for i in range(0,9)]]

return True if board[fooa][foob] == board[bara][barb] else False