TheAlgorithms-C/numerical_methods/lagrange_theorem.C

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main()
{
	float x[20], y[20], a, sum, p;
	int n, i, j;

	printf("Enter the no of entry to insert->");
	scanf("%d", &n);

	for (i = 0; i < n; i++)
	{
		printf("enter the value of x%d->", i);
		scanf("%f", &x[i]);
		printf("enter the value of y%d->", i);
		scanf("%f", &y[i]);
	}
	printf("\n X \t\t Y \n");
	printf("----------------------------\n");
	for (i = 0; i < n; i++)
	{
		printf("%f\t", x[i]);
		printf("%f\n", y[i]);
	}
	printf("\nenter the value of x for interpolation:");
	scanf("%f", &a);
	sum = 0;
	for (i = 0; i < n; i++)
	{
		p = 1.0;
		for (j = 0; j < n; j++)
		{

			if (i != j)
			{
				p = p * (a - x[j]) / (x[i] - x[j]);
			}
			sum = sum + y[i] * p;
		}
		printf("ans is->%f", sum);

		return 0;
	}
}