Write a program (or explain how to do it) that will display a descending "spiral" of NxN numbers, using constant space (no arrays allowed). For example, here's what the spiral looks like for N=10:

   99    98    97    96    95    94    93    92    91    90
   64    63    62    61    60    59    58    57    56    89
   65    36    35    34    33    32    31    30    55    88
   66    37    16    15    14    13    12    29    54    87
   67    38    17     4     3     2    11    28    53    86
   68    39    18     5     0     1    10    27    52    85
   69    40    19     6     7     8     9    26    51    84
   70    41    20    21    22    23    24    25    50    83
   71    42    43    44    45    46    47    48    49    82
   72    73    74    75    76    77    78    79    80    81

(In reply to re: FULL SOLUTION (in C) by SilverKnight)

For odd n, I notice the spiral starts off with 0, 1, going to the left instead of the right.

Lets see if the pre tag works this time:

C:\tc\BIN>spirals 7


48      47      46      45      44      43      42


25      24      23      22      21      20      41


26      9       8       7       6       19      40


27      10      1       0       5       18      39


28      11      2       3       4       17      38


29      12      13      14      15      16      37


30      31      32      33      34      35      36





C:\tc\BIN>spirals 8


63      62      61      60      59      58      57      56


36      35      34      33      32      31      30      55


37      16      15      14      13      12      29      54


38      17      4       3       2       11      28      53


39      18      5       0       1       10      27      52


40      19      6       7       8       9       26      51


41      20      21      22      23      24      25      50


42      43      44      45      46      47      48      49

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Posted by Charlie on 2003-08-21 16:51:49