June 2018 Update

Task/Spiral-matrix/Scilab/spiral-matrix.scilab

@@ -1,22 +1,25 @@
-// Spiral Matrix
-n=10
-mat=zeros(n,n);
-botcol=1; topcol=n
-botrow=1; toprow=n
-ndir=0; col=1; row=1;
-for i=0:n*n-1
-   mat(row,col)=i;
-   if ndir==0
-      if col<topcol then col=col+1; else ndir=1, row=row+1; botrow=botrow+1; end
-   elseif ndir==1
-      if row<toprow then row=row+1; else ndir=2, col=col-1; topcol=topcol-1; end
-   elseif ndir==2
-      if col>botcol then col=col-1; else ndir=3, row=row-1; toprow=toprow-1; end
-   elseif ndir==3
-      if row>botrow then row=row-1; else ndir=0, col=col+1; botcol=botcol+1; end
-   end
-end i
-printf("n=%4d\n",n);
-for i=1:n;
-   for j=1:n; printf("%4d",mat(i,j)); end j; printf("\n");
-end i;
+function a = spiral(n)
+  a = ones(n*n, 1)
+  v = ones(n, 1)
+  u = -n*v;
+  i = n
+  for k = n-1:-1:1
+    j = 1:k
+    u(j) = -u(j)
+    a(j+i) = u(j)
+    v(j) = -v(j)
+    a(j+(i+k)) = v(j)
+    i = i+2*k
+  end
+  a(cumsum(a)) = (1:n*n)'
+  a = matrix(a, n, n)'-1
+endfunction
+
+-->spiral(5)
+ ans  =
+
+    0.     1.     2.     3.     4.
+    15.    16.    17.    18.    5.
+    14.    23.    24.    19.    6.
+    13.    22.    21.    20.    7.
+    12.    11.    10.    9.     8.