Data commit

Task/Spiral-matrix/Maxima/spiral-matrix.maxima

@@ -0,0 +1,40 @@
+spiral(n) := block([a, i, j, k, p, di, dj, vi, vj, imin, imax, jmin, jmax],
+a: zeromatrix(n, n),
+vi: [1, 0, -1, 0],
+vj: [0, 1, 0, -1],
+imin: 0,
+imax: n,
+jmin: 1,
+jmax: n + 1,
+p: 1,
+di: vi[p],
+dj: vj[p],
+i: 1,
+j: 1,
+for k from 1 thru n*n do (
+   a[j, i]: k,
+   i: i + di,
+   j: j + dj,
+   if i < imin or i > imax or j < jmin or j > jmax then (
+      i: i - di,
+      j: j - dj,
+      p: mod(p, 4) + 1,
+      di: vi[p],
+      dj: vj[p],
+      i: i + di,
+      j: j + dj,
+      if p = 1 then imax: imax - 1
+      elseif p = 2 then jmax: jmax - 1
+      elseif p = 3 then imin: imin + 1
+      else jmin: jmin + 1
+   )
+),
+a
+)$
+
+spiral(5);
+/* matrix([ 1,  2,  3,  4,  5],
+          [16, 17, 18, 19,  6],
+          [15, 24, 25, 20,  7],
+          [14, 23, 22, 21,  8],
+          [13, 12, 11, 10,  9]) */