非是非
Thinking, Express

测验题目

问题：

矩阵式螺旋输出:

  1 16 15 14 13
  2 17 24 23 12
  3 18 25 22 11
  4 19 20 21 10
  5  6  7  8  9

参考答案：

<?php

function n_at($N, $r, $c, $s=1){
 $v = 0;

 if($c==1){
   $v = $s + ($r-1);
 }else if($r==$N){
   $v = $s + ($N-1) + ($c-1);
 }else if($c==$N){
   $v = $s + ($N-1) + ($N-1) + ($N-$r);
 }else{
     $v = $s+($N-1)*3 + ($N-$c);
 }
 return $v;
}

function print_square($N){
  $o = ($N+1)/2;
  for($r=1; $r<=$N; $r++){
    for($c=1; $c<=$N; $c++){
      $n_loop  = max(abs($r-$o),abs($c-$o));
      $n_size  = $n_loop*2 + 1;
      $ir = ($r-$o) + ($n_size+1)/2;
      $ic = ($c-$o) + ($n_size+1)/2;
      $s = $N*$N - $n_size*$n_size+1;
      $v = n_at($n_size, $ir, $ic, $s);
      printf("%3d",$v);
    }
    print("\n");
  }
}

print_square(5);

?>

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