【Kata Daily 190912】Alphabetical Addition（字母相加）

题目：

Your task is to add up letters to one letter.

The function will be given a variable amount of arguments, each one being a letter to add.

Notes:

• Letters will always be lowercase.
• Letters can overflow (see second to last example of the description)
• If no letters are given, the function should return 'z'

Examples:

add_letters('a', 'b', 'c') = 'f'
add_letters('a', 'b') = 'c'
add_letters('z') = 'z'
add_letters('z', 'a') = 'a'
add_letters('y', 'c', 'b') = 'd' # notice the letters overflowing
add_letters() = 'z'

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题目大意：字母a-z代表了1-26，给定一个list，将里面字母对应的数字加起来的值对应到字母中。

解题思路：

def add_letters(*letters):
    # your code here
    if letters == '' or letters == 'z':
        return 'z'
    else:
        dic = {'a':1, 'b':2, 'c':3, 'd':4, 'e':5, 'f':6, 'g':7, 'h':8, 'i':9, 'j':10, 'k':11, 'l':12, 'm':13, 'n':14, 'o':15, 'p':16,
        'q':17, 'r':18, 's':19, 't':20, 'u':21, 'v':22, 'w':23, 'x':24, 'y':25, 'z':26}
        dic2 = {1:'a', 2:'b', 3:'c', 4:'d', 5:'e', 6:'f', 7:'g', 8:'h', 9:'i', 10:'j', 11:'k', 12:'l', 13:'m', 14:'n', 15:'o', 16:'p',
        17:'q', 18:'r', 19:'s', 20:'t', 21:'u', 22:'v', 23:'w', 24:'x', 25:'y', 26:'z'}
        sum = 0
        for i in letters:
            sum += dic[i]
        res = sum % 26
        if res == 0:
            return 'z'
        else:
            return dic2[res]

个人的代码总是那么的不堪入目啊 QAQ。基本思路是：做两个字典，分别将字母和数字为key值，然后将数值相加后取余，得到的数字再对应到字母表。

看一下网友们的答案：

num = 'abcdefghijklmnopqrstuvwxyz'
def add_letters(*letters):
    x = 0
    x = sum(num.index(i)+1 for i in letters)
    while x-1 > 25:
        x -= 26
        
    return num[x-1]

另一种：

def add_letters(*letters):
    return chr( (sum(ord(c)-96 for c in letters)-1)%26 + 97)

知识点：

1、ord(c) 将c转为数字，chr(c)将c转为ASCII表中的字母

2、def add_letters(*letters)：带星号是代表传入元组