Python 101

# anagram('dog', 'god') should return True

def distill(x):
    return sorted(list(x.replace(' ','').lower()))

def is_anagram(s1, s2):
    s1 = distill(s1)
    s2 = distill(s2)
    return s1 == s2

is_anagram('clint eastwood','old west action')


#####################################


def pair_sum(arr, k):
    if len(arr)<2:
        return

    seen = set()
    output = set()

    for num in arr:
        target = k-num

        if target not in seen:
            seen.add(num)
        else:
            output.add((min(num,target), max(num,target)))
            # min and max - to arrange the items is ascending order. .. e.g. (1,4), (2,3)

    return len(output)

pair_sum([1,3,2,2,5,-1],4)



#####################################


def finder(arr1, arr2):
    #where arr2 is shuffled arr1 with a random item removed
    arr1.sort()
    arr2.sort()

    for num1, num2 in zip(arr1, arr2):
        # zip joins 2 tuples so that the first item is made of the first item of the zip is made of
        # the first item of the first tuple AND the first item of the second tuple
        if num1 != num2:
            return num1

    return arr1[-1] # last element in the array

arr1 = [1,2,3,4,5,6,7]
arr2 = [3,7,2,1,4,6]
finder(arr1, arr2)


#####################################

import collections

def finder2(arr1, arr2):
    d = collections.defaultdict(int)
    for num in arr2:
        d[num] += 1
    for num in arr1:
        if d[num] == 0:
            return num
        else:
            d[num] -= 1

arr1 = [1,2,3,4,5,6,7]
arr2 = [3,7,2,1,4,6]
finder2(arr1, arr2)



#########################
# Largest continuous sum
#########################
def large_cont_sum(arr):
    if len(arr) == 0:
        return 0

    max_sum = current_sum = arr[0]

    for num in arr[1:]: # arr[1:] skips the first element because it is in the previous line
        current_sum = max(current_sum+num, num)
        max_sum = max(current_sum, max_sum)

    return max_sum

large_cont_sum([1,2,-1,3,4,10,10,-10,-1])



###################
# Sentence reversal
###################
sentence = '   June the   force   be with   you  '
" ".join(reversed(sentence.strip().split()))
# it works, but we need to "show work"
# hence a more complicated version:

def rev_words(s):
    words = []
    length = len(s)
    spaces = [' ']
    i = 0
    while i < length:
        if s[i] not in spaces:
            word_start = i
            while i < length and s[i] not in spaces:
                i += 1
            words.append(s[word_start:i])
        i += 1
    return ' '.join(reversed(words))
rev_words('Hello John how are you')


###########################
# 'Compress' a string
###########################
# AAAAAABBBBBCCCCDD => A5B4C4D2
# case-sensitive
# AAB => A2B1

def compress(s):
    r = ""
    l = len(s)

    if l == 0:
        return ""
    if l == 1:
        return s+"1"

    last = s[0]
    cnt = 1
    i = 1

    while i < l:

        if s[i] == s[i-1]:
            cnt += 1
        else:
            r = r + s[i-1] + str(cnt)
            cnt = 1

        i += 1

    r = r + s[i-1] + str(cnt)

    return r

compress("AAaaaBBBBcDD")



###############################
# Unique characters in a string
###############################

# built-in way:

def all_chars_unique(s):
    return len(set(s)) == len(s)

all_chars_unique('abcdeb')

# our own way:

def unichar2(s):
    chars = set()
    for letter in s:
        if letter in chars:
            return False
        else:
            chars.add(letter)
    return True
unichar2('abcdcef')