Data commit

Task/Jacobi-symbol/Java/jacobi-symbol.java

@@ -0,0 +1,49 @@
+public class JacobiSymbol {
+
+    public static void main(String[] args) {
+        int max = 30;
+        System.out.printf("n\\k ");
+        for ( int k = 1 ; k <= max ; k++ ) {
+            System.out.printf("%2d  ", k);
+        }
+        System.out.printf("%n");
+        for ( int n = 1 ; n <= max ; n += 2 ) {
+            System.out.printf("%2d  ", n);
+            for ( int k = 1 ; k <= max ; k++ ) {
+                System.out.printf("%2d  ", jacobiSymbol(k, n));
+            }
+            System.out.printf("%n");
+        }
+    }
+
+
+    //  Compute (k n), where k is numerator
+    private static int jacobiSymbol(int k, int n) {
+        if ( k < 0 || n % 2 == 0 ) {
+            throw new IllegalArgumentException("Invalid value. k = " + k + ", n = " + n);
+        }
+        k %= n;
+        int jacobi = 1;
+        while ( k > 0 ) {
+            while ( k % 2 == 0 ) {
+                k /= 2;
+                int r = n % 8;
+                if ( r == 3 || r == 5 ) {
+                    jacobi = -jacobi;
+                }
+            }
+            int temp = n;
+            n = k;
+            k = temp;
+            if ( k % 4 == 3 && n % 4 == 3 ) {
+                jacobi = -jacobi;
+            }
+            k %= n;
+        }
+        if ( n == 1 ) {
+            return jacobi;
+        }
+        return 0;
+    }
+
+}