#!/usr/bin/env python
# coding: utf-8

# # Chapter 15 Practice Makes Perfect
# 
# 
# <img align="left" src="https://i.imgur.com/lnc0qMV.png" />

# In[1]:


# 01 연습이 최고를 만듭니다
# there is nothing in this lesson
pass


# In[2]:


# 02 짝수인지 확인하기

def is_even(x):
    return x % 2 == 0
    
print (is_even(2))
print (is_even(13))


# In[3]:


# 03 정수인지 확인하기

from math import floor
def is_int(x):
    if floor(x) == x:
        return True
    else:
        return False
    
print (is_int(10.1))


# In[4]:


# 04 숫자들의 합

def digit_sum(n):
    ans = 0
    while n > 0:
        ans += n % 10
        n = floor(n / 10)  # 원문은 2.7 기준
    return ans

print (digit_sum(3233))

# 참고)
# Python3에서 int/int 값은 float가 됩니다.
# Python2에서 int/int 값은 int 됩니다.


# In[5]:


# 05 팩토리얼(factorial)

def factorial(x):
    ans = 1
    while x > 0:
        ans *= x
        x -= 1
    return ans

print (factorial(10))


# In[6]:


# 06 소수인지 확인하기

def is_prime(x):
    if x <= 1:
        return False
    for i in range(2, x):
        if x % i == 0:
            return False
    return True

print (is_prime(13))


# In[7]:


# 07 문자열 뒤집기

def reverse(s):
    res = ""
    for i in range(len(s) - 1, -1, -1):
        res += s[i]
    return res

print (reverse("hello"))
# KT의 브랜드 olleh가 hello를 reverse 한 것이죠


# In[8]:


# 08 자음 걸러내기

def is_vowel(c):
    c = c.lower()
    if c == 'a' or c == 'e' or c == 'i' or c == 'o' or c == 'u':
        return True
    else:
        return False

def anti_vowel(text):
    res = ""
    for i in range(0, len(text)):
        if not is_vowel(text[i]):
            res += text[i]
    return res
    
print (anti_vowel('this is test text'))


# In[9]:


# 09 스크래블 게임

score = {"a": 1, "c": 3, "b": 3, "e": 1, "d": 2, "g": 2,
    "f": 4, "i": 1, "h": 4, "k": 5, "j": 8, "m": 3,
    "l": 1, "o": 1, "n": 1, "q": 10, "p": 3, "s": 1,
    "r": 1, "u": 1, "t": 1, "w": 4, "v": 4, "y": 4,
    "x": 8, "z": 10}

def scrabble_score(word):
    word = word.lower()
    ans = 0
    for c in word:
        ans += score[c]
    return ans

print (scrabble_score('cansentme'))


# In[10]:


# 10 문자열 검열

"""
method 1: normal way to finish this task
"""
def censor(text, word):
    strings = text.split()
    for i in range(0, len(strings)):
        if strings[i] == word:
            strings[i] = "*" * len(word)
    return " ".join(strings)



"""
method 2: use KMP algorithm, but it's like employing a steam engine to crack a nut
"""
def get_next_array(word):
    nxt = [-1]
    for i in range(1, len(word)):
        n = nxt[i - 1]
        nxt.append(-1)
        while n != -1:
            if word[n + 1] == word[i]:
                nxt[i] = n + 1
                break
            n = nxt[n]
        if n == -1 and word[0] == word[i]:
            nxt[i] = 0
    return nxt

def KMP(text, word, nxt, i):
    j = 0
    while i < len(text) and j < len(word):
        while j != -1 and text[i] != word[j]:
            if j == 0:
                j = -1
            else:
                j = nxt[j-1] + 1
        i += 1
        j += 1
    if j == len(word):
        return i
    return -1

def censor(text, word): #use KMP algorithm
    nxt = get_next_array(word)
    i = 0
    while i < len(text) and i != -1:
        i = KMP(text, word, nxt, i)
        if i == -1:
            break;
        newtext = text[0: i - len(word)] + "*" * len(word) + text[i :]
        text = newtext
    return text
    

print(censor("this is test text", 'test'))
    
# KMP: Knuth Morris Partt 이름을 따서 만들어진 문자열 검색 알고리즘


# In[11]:


# 11 요소의 갯수 세기

def count(sequence, item):
    return sequence.count(item)

print(count("this is test text", 't'))


# In[12]:


# 12 요소 걸러내기

def purify(lst):
    res = []
    for e in lst:
        if e % 2 == 0:
            res.append(e)
    return res
    
print(purify([2, 34, 67, 32, 12, 79]))


# In[13]:


# 13 곱셈

def product(lst):
    res = 1
    for e in lst:
        res *= e
    return res

print(product([2, 34, 67, 32, 12, 79]))


# In[14]:


# 14 중복 요소 제거하기

def remove_duplicates(lst):
    res = []
    for e in lst:
        if e not in res:
            res.append(e)
    return res

print(remove_duplicates([2, 12, 67, 2, 12]))


# In[15]:


# 15 중앙값

def median(lst):
    lst2 = sorted(lst)
    length = len(lst2)
    if length % 2 == 0:
        return (lst2[int(length / 2)] + lst2[int(length / 2 - 1)]) / 2.0
    else:
        return lst2[int(length / 2)]
        

print(median([2, 12, 67, 2, 12]))