1. #include<bits/stdc++.h>
    2. using namespace std;
    4. static string alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
    5. //双表代替加密
    7. //第一种加密
    8. int first_change(char& letter)
    9. {
    10.     int location;
    11.     string key1 = "qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM";
    12.     //string alphabet = "abcdefghijklmnopqrstuvwxyz";
    13.     if (letter != ' ')
    14.     {
    15.         location = alphabet.find_first_of(letter);
    16.         letter = key1[location];
    17.     }
    18.     return 1;
    19. }
    21. //第二种加密
    22. int second_change(char& letter)
    23. {
    24.     int location;
    25.     string key2 = "lkjhgfdsaqwertyuiopmnbzxcvLKJHGFDSAQWERTYUIOPMNBZXCV";
    26.     //string alphabet = "abcdefghijklmnopqrstuvwxyz";
    27.     if (letter != ' ')
    28.     {
    29.         location = alphabet.find_first_of(letter);
    30.         letter = key2[location];
    31.     }
    32.     return 1;
    33. }
    35. //加密时：判断该字母第几次出现在句子当中
    36. int judeg_encryption(const char letter)
    37. {
    38.     static map<char, int> letter_nums
    39.     {
    40.         {'a',0},{'b',0},{'c',0},{'d',0},{'e',0},{'f',0},
    41.         {'g',0},{'h',0},{'i',0},{'g',0},{'k',0},{'l',0},
    42.         {'m',0},{'n',0},{'o',0},{'p',0},{'q',0},{'r',0},
    43.         {'s',0},{'t',0},{'u',0},{'v',0},{'w',0},{'x',0},
    44.         {'y',0},{'z',0},
    45.         {'A',0},{'B',0},{'C',0},{'D',0},{'E',0},{'F',0},
    46.         {'G',0},{'H',0},{'I',0},{'G',0},{'K',0},{'L',0},
    47.         {'M',0},{'N',0},{'O',0},{'P',0},{'Q',0},{'R',0},
    48.         {'S',0},{'T',0},{'U',0},{'V',0},{'W',0},{'X',0},
    49.         {'Y',0},{'Z',0}
    50.     };
    51.     if (letter != ' ')
    52.     {
    53.         letter_nums[letter]++;
    54.     }
    56.     return letter_nums[letter] % 2;
    57.     //若返回值为1，对应第一次加密方法
    58.     //若返回值为0，对应第二次加密方法
    59. }
    61. //加密
    62. string encryption(string& sentence, vector<int>& record)
    63. {
    64.     char letter;
    65.     int option;             //接受选择判断函数的返回值
    66.     for (int i = 0; i < sentence.length(); i++)
    67.     {
    68.         if (sentence[i] != ' ')
    69.         {
    70.             letter = sentence[i];
    71.             option = judeg_encryption(letter);
    72.             if (option == 1)
    73.             {
    74.                 first_change(letter);
    75.                 sentence[i] = letter;
    76.                 record.push_back(1);
    78.             }
    79.             if (option == 0)
    80.             {
    81.                 second_change(letter);
    82.                 sentence[i] = letter;
    83.                 record.push_back(0);
    84.             }
    85.         }
    86.     }
    87.     return sentence;
    88. }
    90. //第一种解密
    91. int first_decode(char& letter)
    92. {
    93.     int location;
    94.     string key1 = "qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM";
    95.     //string alphabet = "abcdefghijklmnopqrstuvwxyz";
    96.     if (letter != ' ')
    97.     {
    98.         location = key1.find_first_of(letter);
    99.         letter = alphabet[location];
    100.     }
    101.     return 1;
    102. }
    103. //第二种解密
    104. int second_decode(char& letter)
    105. {
    106.     int location;
    107.     string key2 = "lkjhgfdsaqwertyuiopmnbzxcvLKJHGFDSAQWERTYUIOPMNBZXCV";
    108.     //string alphabet = "abcdefghijklmnopqrstuvwxyz";
    109.     if (letter != ' ')
    110.     {
    111.         location = key2.find_first_of(letter);
    112.         letter = alphabet[location];
    113.     }
    114.     return 1;
    115. }
    118. string decode(string& sentence, const vector<int> record)
    119. {
    120.     char letter;
    121.     int j = 0;
    122.     for (int i = 0; i < sentence.length(); i++)
    123.     {
    124.         if (sentence[i] != ' ')
    125.         {
    126.             if (record[j] == 1)
    127.             {
    128.                 letter = sentence[i];
    129.                 first_decode(letter);
    130.                 sentence[i] = letter;
    131.             }
    132.             if (record[j] == 0)
    133.             {
    134.                 letter = sentence[i];
    135.                 second_decode(letter);
    136.                 sentence[i] = letter;
    137.             }
    138.             j++;
    139.         }
    140.     }
    141.     return sentence;
    142. }
    145. int main()
    146. {
    147.     static vector<int> record;
    149.     string sentence;
    150.     cout << "please input what you want to encrypt:" << endl;
    151.     getline(cin, sentence);
    154.     cout << "加密后" << endl;
    155.     cout << encryption(sentence, record) << endl;
    157.     cout << "解密后" << endl;
    158.     cout << decode(sentence, record);
    159. }