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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10.     public static void main(String[] args) {
  11.         int[] testvals = {Integer.MIN_VALUE, Integer.MAX_VALUE, 123456789, 987654321, -123456789, -987654321};
  12.         for (int i = -50; i <= 50; i++) {
  13.             System.out.printf("Digital sum of %5d is %5d\n", i, computeDigitalRoot(i));
  14.         }
  15.         for (int i : testvals) {
  16.             System.out.printf("Digital sum of %5d is %5d\n", i, computeDigitalRoot(i));
  17.         }
  18.     }
  19.  
  20.     private static int computeDigitalRoot(int num) {
  21.  
  22.         if (num < 10 && num > -10) {
  23.             return Math.abs(num);
  24.         }
  25.  
  26.         int sum = 0;
  27.         while (num != 0) {
  28.             // abs needed to cope with negative input values
  29.             sum += Math.abs(num % 10);
  30.             num /= 10;
  31.         }
  32.  
  33.         return computeDigitalRoot(sum);
  34.     }
  35. }
Success #stdin #stdout 0.09s 380544KB
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stdin
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Standard input is empty
stdout
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Digital sum of   -50 is     5
Digital sum of   -49 is     4
Digital sum of   -48 is     3
Digital sum of   -47 is     2
Digital sum of   -46 is     1
Digital sum of   -45 is     9
Digital sum of   -44 is     8
Digital sum of   -43 is     7
Digital sum of   -42 is     6
Digital sum of   -41 is     5
Digital sum of   -40 is     4
Digital sum of   -39 is     3
Digital sum of   -38 is     2
Digital sum of   -37 is     1
Digital sum of   -36 is     9
Digital sum of   -35 is     8
Digital sum of   -34 is     7
Digital sum of   -33 is     6
Digital sum of   -32 is     5
Digital sum of   -31 is     4
Digital sum of   -30 is     3
Digital sum of   -29 is     2
Digital sum of   -28 is     1
Digital sum of   -27 is     9
Digital sum of   -26 is     8
Digital sum of   -25 is     7
Digital sum of   -24 is     6
Digital sum of   -23 is     5
Digital sum of   -22 is     4
Digital sum of   -21 is     3
Digital sum of   -20 is     2
Digital sum of   -19 is     1
Digital sum of   -18 is     9
Digital sum of   -17 is     8
Digital sum of   -16 is     7
Digital sum of   -15 is     6
Digital sum of   -14 is     5
Digital sum of   -13 is     4
Digital sum of   -12 is     3
Digital sum of   -11 is     2
Digital sum of   -10 is     1
Digital sum of    -9 is     9
Digital sum of    -8 is     8
Digital sum of    -7 is     7
Digital sum of    -6 is     6
Digital sum of    -5 is     5
Digital sum of    -4 is     4
Digital sum of    -3 is     3
Digital sum of    -2 is     2
Digital sum of    -1 is     1
Digital sum of     0 is     0
Digital sum of     1 is     1
Digital sum of     2 is     2
Digital sum of     3 is     3
Digital sum of     4 is     4
Digital sum of     5 is     5
Digital sum of     6 is     6
Digital sum of     7 is     7
Digital sum of     8 is     8
Digital sum of     9 is     9
Digital sum of    10 is     1
Digital sum of    11 is     2
Digital sum of    12 is     3
Digital sum of    13 is     4
Digital sum of    14 is     5
Digital sum of    15 is     6
Digital sum of    16 is     7
Digital sum of    17 is     8
Digital sum of    18 is     9
Digital sum of    19 is     1
Digital sum of    20 is     2
Digital sum of    21 is     3
Digital sum of    22 is     4
Digital sum of    23 is     5
Digital sum of    24 is     6
Digital sum of    25 is     7
Digital sum of    26 is     8
Digital sum of    27 is     9
Digital sum of    28 is     1
Digital sum of    29 is     2
Digital sum of    30 is     3
Digital sum of    31 is     4
Digital sum of    32 is     5
Digital sum of    33 is     6
Digital sum of    34 is     7
Digital sum of    35 is     8
Digital sum of    36 is     9
Digital sum of    37 is     1
Digital sum of    38 is     2
Digital sum of    39 is     3
Digital sum of    40 is     4
Digital sum of    41 is     5
Digital sum of    42 is     6
Digital sum of    43 is     7
Digital sum of    44 is     8
Digital sum of    45 is     9
Digital sum of    46 is     1
Digital sum of    47 is     2
Digital sum of    48 is     3
Digital sum of    49 is     4
Digital sum of    50 is     5
Digital sum of -2147483648 is     2
Digital sum of 2147483647 is     1
Digital sum of 123456789 is     9
Digital sum of 987654321 is     9
Digital sum of -123456789 is     9
Digital sum of -987654321 is     9
https://ideone.com/igYAZA
language:
Java (12.0.1)
created:
9 years ago
visibility:
public

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