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 12032011, 12:29 PM #1Member
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Need an explanation regards the following recursion
Hi, need help understanding the calculation aspect of: if ((q[i]  q[n]) == (n  i)) return false; // same major diagonal
in the following code:
Java Code:public class Queens { /*********************************************************************** * Return true if queen placement q[n] does not conflict with * other queens q[0] through q[n1] ***********************************************************************/ public static boolean isConsistent(int[] q, int n) { for (int i = 0; i < n; i++) { if (q[i] == q[n]) return false; // same column if ((q[i]  q[n]) == (n  i)) return false; // same major diagonal if ((q[n]  q[i]) == (n  i)) return false; // same minor diagonal } return true; }
Thanks :)
 12032011, 02:01 PM #2
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Re: Need an explanation regards the following recursion
Draw an eight x eight grid on a piece of paper; the top row of your grid contains the coordinates (0, 0) (0, 1) (0, 2) (0, 3) (0, 4) (0, 5) (0, 6) and (0, 7); the next row contains the coordinates (1, 0) (1, 1) (1, 2) ... etc. Supose your array q contains eight elements, one for each column in your grid and q[i] contains the second coordinate in the coordinate pair (i, q[i]).
If q[i] ==q[n] there are two queens in columns i and n that are positioned in the same row. Check your grid and try to find a regularity for two values in the same upgoing diagonal and similar for a down going diagonal.
kind regards,
JosBuild a wall around Donald Trump; I'll pay for it.
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