Task 9 is done

2025.05.02/dist/Krivoruchenko_SK/solve.c

@@ -293,3 +293,49 @@ int t8_solve (
 
 	return it;
 }
+
+int t9_solve (
+		double (*f) (double), 
+		double a, double b, 
+		double eps, int m, double *x
+) {
+	const double gdrt = 2 / (1 + sqrt(5));
+	int it = 0;
+
+	double x_1 = b + (a - b) * gdrt, x_2 = a + (b - a) * gdrt;
+	double y_1 = f(x_1), y_2 = f(x_2);
+
+	for (it = 1; it <= m; ++it)
+	{
+		if (y_1 - y_2 > DBL_EPSILON)
+		{
+			b = x_2;
+
+			x_2 = x_1;
+			y_2 = y_1;
+
+			x_1 = b + (a - b) * gdrt;
+			y_1 = f(x_1);
+		} else
+		{
+			a = x_1;
+
+			x_1 = x_2;
+			y_1 = y_2;
+
+			x_2 = a + (b - a) * gdrt;
+			y_2 = f(x_2);
+		}
+
+		if (fabs(b - a) < eps)
+		{
+			*x = x_1;
+			break;
+		}
+	}
+
+	if (it > m)
+		it = -1;
+
+	return it;
+}