tasks a-s

Task/Nth-root/Java/nth-root-1.java

@@ -0,0 +1,18 @@
+public static double nthroot(int n, double A) {
+	return nthroot(n, A, .001);
+}
+public static double nthroot(int n, double A, double p) {
+	if(A < 0) {
+		System.err.println("A < 0");// we handle only real positive numbers
+		return -1;
+	} else if(A == 0) {
+		return 0;
+	}
+	double x_prev = A;
+	double x = A / n;  // starting "guessed" value...
+	while(Math.abs(x - x_prev) > p) {
+		x_prev = x;
+		x = ((n - 1.0) * x + A / Math.pow(x, n - 1.0)) / n;
+	}
+	return x;
+}

Task/Nth-root/Java/nth-root-2.java

@@ -0,0 +1,15 @@
+public static double nthroot(int n, double x) {
+  assert (n > 1 && x > 0);
+  int np = n - 1;
+  double g1 = x;
+  double g2 = iter(g1, np, n, x);
+  while (g1 != g2) {
+    g1 = iter(g1, np, n, x);
+    g2 = iter(iter(g2, np, n, x), np, n, x);
+  }
+  return g1;
+}
+
+private static double iter(double g, int np, int n, double x) {
+  return (np * g + x / Math.pow(g, np)) / n;
+}