Start Task 2

2025.04.18/02Ex/solve.c

@@ -0,0 +1,56 @@
+#include "solve.h"
+
+#include <float.h>
+#include <math.h>
+#include <stdio.h>
+
+// the Newton interpolation polynomial
+double t2_solve (const double x_0, const int n, const double * restrict X, double * restrict Y)
+{
+	double last_x = X[n-1];
+	double last_y = Y[n-1];
+	
+	double value = 0;
+	double start_value = 0;
+
+	for (int k = 0; k < n-1; ++k)
+	{
+		printf ("------- K = %d -------\n", k);
+
+		for (int i = n-2; i >= k; --i)
+		{
+			const double x_i = X[i-k];
+			const double y_i = Y[i];
+			
+			if (fabs(last_x - x_i) < DBL_EPSILON)
+				return DBL_MAX;
+			
+//			printf ("Y[%d] = (%lf - %lf) / (%lf - %lf)\n", i+1, last_y, y_i, last_x, x_i);
+			Y[i+1] = (last_y - y_i) / (last_x - x_i);
+			printf ("I = %d, f(x%d, ... , x%d) = %lf\n", i, i-k+1, i+2, Y[i]);
+
+			last_x = x_i;
+			last_y = y_i;
+		}
+
+		last_x = X[n-1];
+		last_y = Y[n-1];
+	}
+
+	last_x = X[0];
+	start_value = 1;
+	value = Y[0];
+
+	for (int i = 1; i < n; ++i)
+	{
+		start_value *= (x_0 - last_x);
+		if (fabs(Y[i]) > DBL_EPSILON) 
+			value += Y[i] * start_value;
+		printf ("i = %d, start_value = %lf, value = %lf, last_x = %lf\n", i, start_value, value, last_x);
+		printf ("Y[%d] = %lf\n", i, Y[i]);
+		last_x = X[i];
+	}
+
+	return value;
+}
+