samples/alpha-mj-exp/Palindromes.mj

   1 program Palindromes {
   2     // return a palindrome if it can be generated from given letters
   3
   4     char[] load()
   5                 char[] res;
   6         char in;
   7                 int c, num; {
   8                 print('l');
   9                 print('?');
  10                 read(num);
  11                 res = new char[num];
  12                 c = 0;
  13                 while (c<num) {
  14                         print(c);
  15                         print('?');
  16                         read(in);
  17                         if (ord(in) == 10) {
  18                             read(in);
  19                         }
  20                         res[c] = in;
  21                         c++;
  22                 }
  23                 return res;
  24         }
  25
  26     char[] reverse(char[] arr)
  27     int i;
  28     char[] res;
  29     {
  30         res = new char[len(arr)];
  31         i = 0;
  32         while (i < len(arr)) {
  33             res[i] = arr[len(arr) - i - 1];
  34             i++;
  35         }
  36         return res;
  37     }
  38
  39     void printArr(char[] arr)
  40     int i;
  41     {
  42         print('[');
  43         if (arr != null) {
  44             i = 0;
  45             while (i < len(arr)) {
  46                 print(arr[i], 3);
  47                 i++;
  48             }
  49         }
  50         print(']', 3);
  51         print('\n');
  52     }
  53
  54     char[] concatA(char[] arr1, char[] arr2)
  55     char[] res;
  56     int i;
  57     {
  58         res = new char[len(arr1) + len(arr2)];
  59         i = 0;
  60         while (i < len(arr1)) {
  61             res[i] = arr1[i];
  62             i++;
  63         }
  64         while (i < len(res)) {
  65             res[i] = arr2[i - len(arr1)];
  66             i++;
  67         }
  68
  69         return res;
  70     }
  71
  72     char[] copy(char[] arr, int counter)
  73     int i;
  74     char[] res;
  75     {
  76         res = new char[counter];
  77         i = 0;
  78         while (i < len(res)) {
  79             res[i] = arr[i];
  80             i++;
  81         }
  82
  83         return res;
  84     }
  85
  86     char[] concatC(char[] arr, char character)
  87     char[] res;
  88     int i;
  89     {
  90         res = new char[len(arr) + 1];
  91         i = 0;
  92         while (i < len(arr)) {
  93             res[i] = arr[i];
  94             i++;
  95         }
  96         res[i] = character;
  97
  98         return res;
  99     }
 100
 101     char[] findPalindrome(char[] s)
 102     int[] letters;
 103     int i, j, counter, ret;
 104     char ch, oddChar;
 105     char[] palindrome, palindromeRes;
 106     {
 107         letters = new int[26];
 108
 109         i = 0;
 110         while (i < len(letters)) {
 111             letters[i] = 0;
 112             i++;
 113         }
 114
 115         i = 0;
 116         while (i < len(s)) {
 117             if (ord(s[i]) >= 97 && ord(s[i]) <= 122) {
 118                 letters[ord(s[i]) - 97]++;
 119             }
 120             i++;
 121         }
 122
 123         oddChar = ' ';
 124         palindrome = new char[len(s)];
 125         counter = 0;
 126
 127         i = 0;
 128         ret = 1;
 129         while (i < len(letters) && ret != 0) {
 130             if (letters[i] > 0 && letters[i] % 2 == 0) {
 131                 j = 1;
 132                 while (j <= letters[i] / 2) {
 133                     palindrome[counter] = chr(i + 97);
 134                     counter++;
 135                     j++;
 136                 }
 137             } else if (letters[i] > 0 && oddChar == ' ') {
 138                 oddChar = chr(i + 97);
 139                 j = 1;
 140                 while (j <= letters[i] / 2) {
 141                     palindrome[counter] = chr(i + 97);
 142                     counter++;
 143                     j++;
 144                 }
 145             } else if (letters[i] % 2 != 0 && oddChar != ' ') {
 146                 ret = 0;
 147             }
 148
 149             i++;
 150         }
 151
 152         palindromeRes = copy(palindrome, counter);
 153
 154         if (ret == 0) {
 155             return null;
 156         } else if (oddChar != ' ') {
 157             return concatA(concatC(palindromeRes, oddChar), reverse(palindromeRes));
 158         } else {
 159             return concatA(palindromeRes, reverse(palindromeRes));
 160         }
 161     }
 162
 163     void main()
 164     char[] input;
 165     int response;
 166     {
 167         input = load();
 168         printArr(input);
 169         printArr(findPalindrome(input));
 170     }
 171 }