Data commit

Task/Jacobi-symbol/Crystal/jacobi-symbol.crystal

@@ -0,0 +1,22 @@
+def jacobi(a, n)
+  raise ArgumentError.new "n must b positive and odd" if n < 1 || n.even?
+  res = 1
+  until (a %= n) == 0
+    while a.even?
+      a >>= 1
+      res = -res if [3, 5].includes? n % 8
+    end
+    a, n = n, a
+    res = -res if a % 4 == n % 4 == 3
+  end
+  n == 1 ? res : 0
+end
+
+puts "Jacobian symbols for jacobi(a, n)"
+puts "n\\a  0  1  2  3  4  5  6  7  8  9 10"
+puts "------------------------------------"
+1.step(to: 17, by: 2) do |n|
+   printf("%2d ", n)
+   (0..10).each { |a| printf(" % 2d", jacobi(a, n)) }
+   puts
+end