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dmilicev

spiral_square_matrix_v1.c

Dec 17th, 2019
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  1. /*
  2.  
  3.     spiral_square_matrix_v1.c       by Dragan Milicev
  4.  
  5.  
  6.     A spiral square matrix of order n x n
  7.  
  8.     starting from the upper left (UL) element M[0][0]
  9.  
  10.     fills in clockwise with numbers from 1 to n*n.
  11.  
  12.  
  13.  Enter the number (2 <= n <= 19) of the rows (columns)
  14.  of the square matrix M[][], n = 4
  15.  
  16.  The matrix M rank is n = 4
  17.  
  18.  Spiral matrix is:
  19.  
  20.    1   2   3   4
  21.  
  22.   12  13  14   5
  23.  
  24.   11  16  15   6
  25.  
  26.   10   9   8   7
  27.  
  28.  
  29.     You can find all my C programs at Dragan Milicev's pastebin:
  30.  
  31.     https://pastebin.com/u/dmilicev
  32.  
  33.     https://www.facebook.com/dmilicev
  34.  
  35. */
  36.  
  37.  
  38. #include <stdio.h>
  39. #include <stdlib.h>
  40.  
  41. #define MAX_SIZE 19         // the highest rank of the matrix M[][]
  42.  
  43.  
  44. // Displays a matrix M[][] that has r rows and c columns
  45. void print_matrix( char *text, int M[][MAX_SIZE], int r, int c )
  46. {
  47.     int i, j;
  48.  
  49.     printf("\n%s\n\n", text );
  50.  
  51.     for(i=0;i<r;i++) {      // print matrix M[][]
  52.         for(j=0;j<c;j++)
  53.             printf("%4d", M[i][j] );
  54.  
  55.         printf("\n\n");     // new matrix row
  56.     }
  57.     printf("\n\n");
  58. }
  59.  
  60.  
  61. // It sets all elements of the matrix M[][] having r rows and c columns to the int number
  62. void set_matrix_elements_to_number( int M[][MAX_SIZE], int r, int c, int number ) {
  63.     int i, j;
  64.  
  65.     for(i=0;i<r;i++)
  66.         for(j=0;j<c;j++)
  67.             M[i][j] = number;
  68. }
  69.  
  70.  
  71. // This problem is simplified by filling in a ring-by-ring matrix.
  72. // We start from the outer edges and fill all four directions separately
  73. // in the order: right, down, left, up.
  74. // Then we fill in the next ring ...
  75. int main(void)
  76. {
  77.     int M[MAX_SIZE][MAX_SIZE], n;
  78.     int number, r, c, r_min, c_min, r_max, c_max;
  79.  
  80.     printf("\n Enter the number (2 <= n <= %d) of the rows (columns) \n of the square matrix M[][], n = ", MAX_SIZE);
  81.     scanf("%d", &n);
  82.     printf("\n\n");
  83.  
  84.     if ( n < 2 || n > MAX_SIZE ) {
  85.         printf("\n Due to the view, it does not make sense for the matrix row \n to be less than 2 or greater than %d !\n", MAX_SIZE);
  86.         exit(1);
  87.     }
  88.  
  89.     printf("\n The matrix M rank is n = %d \n\n",n);
  90.  
  91.     // Set all elements of the matrix M[][] to zero to move around the matrix
  92.     // by checking the condition: while( M[r][c] == 0 )
  93.     set_matrix_elements_to_number(M,n,n,0);
  94.  
  95.     //print_matrix(" The matrix M[][] with zeros is: ", M, n, n);
  96.  
  97.     // initial values
  98.     number = 1;     // the first number to be written in the matrix M[][]
  99.     r = 0;          // current row
  100.     c = 0;          // current column
  101.     r_min = 0;      // minimum row          // current ring boundaries
  102.     c_min = 0;      // minimum column       // current ring boundaries
  103.     r_max = n-1;    // maximum row
  104.     c_max = n-1;    // maximum column
  105.  
  106.     while ( number < n*n ){   // number goes from 1 to n*n
  107.  
  108.         // to the right
  109.         while( M[r][c] == 0  &&  c <= c_max )
  110.             M[r][c++] = number++;
  111.  
  112.         // to the down
  113.         r++;    // we increase the current row because we are going down
  114.         c--;    // we are reducing the current column since we last enlarged it unnecessarily
  115.         while( M[r][c] == 0  &&  r <= r_max )
  116.             M[r++][c] = number++;
  117.  
  118.         // to the left
  119.         r--;    // we are reducing the current row since we last enlarged it unnecessarily
  120.         c--;    // we reduce the current column because we go to the left
  121.         while( M[r][c] == 0  &&  c >= c_min )
  122.             M[r][c--] = number++;
  123.  
  124.         // to the up
  125.         r--;    // we reduce the current row because we go up
  126.         c++;    // we are enlarging the current column since we last reduced it unnecessarily
  127.         while( M[r][c] == 0  &&  r >= r_min )
  128.             M[r--][c] = number++;
  129.  
  130.         r_min++;    // we have filled the outer frame of the matrix M and are now reducing it
  131.         c_min++;
  132.         r_max--;
  133.         c_max--;
  134.  
  135.         r = r_min;  // new starting values for the next inner ring of matrix M
  136.         c = c_min;
  137.     }
  138.  
  139.     // If n is odd, the above algorithm leaves an unfilled last number
  140.     // in the center of the matrix M[n/2][n/2] so let's fill it now:
  141.     if ( n % 2 )   // if n is odd
  142.         M[n/2][n/2] = n*n;
  143.  
  144.     print_matrix(" Spiral matrix is: ", M, n, n);
  145.  
  146.  
  147.     return 0;
  148. }
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