题解 | 字符串加解密

没啥好说的，按照规则一个一个替换就好了，注意一下边界处理。

import sys

_ord_0 = ord("0")
_ord_9 = ord("9")
_ord_a = ord("a")
_ord_z = ord("z")
_ord_A = ord("A")
_ord_Z = ord("Z")
def encode(s):
    result = []
    for each in s:
        t = 0
        cn = ord(each)
        # 特殊处理
        if cn == _ord_9:
            t = _ord_0
        elif cn == _ord_z:
            t = _ord_A
        elif cn == _ord_Z:
            t = _ord_a
        # 通常处理
        else:
            # 如果是数字(非9)
            if _ord_0 <= cn < _ord_9:
                t = cn + 1
            # 如果是小写字母(非z)
            elif _ord_a <= cn < _ord_z:
                t = cn - _ord_a + _ord_A + 1
            # 如果是大写字母(非Z)
            elif _ord_A <= cn < _ord_Z:
                t = cn - _ord_A + _ord_a + 1
        result.append(chr(t))
    return "".join(result)
                
def decode(s):
    result = []
    for each in s:
        t = 0
        cn = ord(each)
        # 特殊处理
        if cn == _ord_0:
            t = _ord_9
        elif cn == _ord_A:
            t = _ord_z
        elif cn == _ord_a:
            t = _ord_Z
        # 通常处理
        else:
            # 如果是数字(非0)
            if _ord_0 < cn <= _ord_9:
                t = cn - 1
            # 如果是小写字母(非a)
            elif _ord_a < cn <= _ord_z:
                t = cn - _ord_a + _ord_A - 1
            # 如果是大写字母(非A)
            elif _ord_A < cn <= _ord_Z:
                t = cn - _ord_A + _ord_a - 1
        result.append(chr(t))
    return "".join(result)

for idx, line in enumerate(sys.stdin):
    a = line.strip()
    if idx == 0:
        print(encode(a))
    elif idx == 1:
        print(decode(a))