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I have a grid: int[][] the_grid = new int[4][4]; and I want to randomly populate it with elements ?, +, -, *, !, /, #, % such that exactly two squares have one of the elements in them. What's the most succinct and efficient way to accomplish this task?

Paul Samsotha
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user3193204
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  • Sorry, I don't really understand... are the elements *?, +, -, *, !, /, #, %* considered as `int`? Or is your grid actually a `String[][]` ? – ccjmne Feb 07 '14 at 05:09
  • Good puzzle. http://stackoverflow.com/a/4040031/2359488 this link shows how to generate random numbers without duplicates. If you populate a list containing 16 elements ( ?, +, -, *, !, /, #, % .. each twice), and then pop them back randomly into your grid, you'd get what you want. – Khulja Sim Sim Feb 07 '14 at 05:14
  • Also, 2 more things: could it possibly be a `char[][]` array; and when you say *exactly two squares have one of the elements in them*, what does that mean? – Alvin Bunk Feb 07 '14 at 05:17

1 Answers1

1

In case your grid actually contains Strings (and not ints), I would simply:

list the tokens you can have: 

final List<String> tokens = Arrays.asList("?", "+", "-", "*", "!", "/", "#", "%", "?", "+", "-", "*", "!", "/", "#", "%");

shuffle these tokens:

Collections.shuffle(tokens);

then finally add them while iterating over your grid:

int i = 0, j = 0;
for (final String token : tokens) {
    theGrid[i][j] = token;
    if (++j == 4) {
        j = 0;
        ++i;
    }
}

Complete example:

final String[][] theGrid = new String[4][4];
final List<String> tokens = Arrays.asList("?", "+", "-", "*", "!", "/", "#", "%", "?", "+", "-", "*", "!", "/", "#", "%");
Collections.shuffle(tokens);

int i = 0, j = 0;
for (final String token : tokens) {
    theGrid[i][j] = token;
    if (++j == 4) {
        j = 0;
        ++i;
    }
}

Usage:

for (final String[] row : theGrid) {
    for (final String column : row) {
        System.out.print(column);
    }

    System.out.println();
}

Sample output (changes every time):

?!!%
+*--
#/#%
*/?+
ccjmne
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