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  1. class Main {
  2.     public static void main(String[] args) {
  3.         double[] x = {0, 1, 2, 3};
  4.         double[] y = {1, 0, 1, 10};
  5.         double X = 0.5;
  6.  
  7.         double result = backwardInterpolation(x, y, X);
  8.         System.out.printf("Interpolated value at x = %.3f is y = %.3f\n", X, result);
  9.     }
  10.  
  11.     static double backwardInterpolation(double[] x, double[] y, double X) {
  12.         int n = x.length;
  13.         double[][] diff = new double[n][n];
  14.  
  15.         for (int i = 0; i < n; i++)
  16.             diff[i][0] = y[i];
  17.  
  18.         for (int j = 1; j < n; j++)
  19.             for (int i = n - 1; i >= j; i--)
  20.                 diff[i][j] = diff[i][j - 1] - diff[i - 1][j - 1];
  21.  
  22.         double h = x[1] - x[0];
  23.         double p = (X - x[n - 1]) / h;
  24.  
  25.         double sum = diff[n - 1][0];
  26.         double term = 1;
  27.  
  28.         for (int i = 1; i < n; i++) {
  29.             term *= (p + (i - 1));
  30.             sum += term * diff[n - 1][i] / fact(i);
  31.         }
  32.  
  33.         return sum;
  34.     }
  35.  
  36.     static int fact(int n) {
  37.         int f = 1;
  38.         for (int i = 2; i <= n; i++) f *= i;
  39.         return f;
  40.     }
  41. }
  42.  
Success #stdin #stdout 0.14s 54048KB
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Standard input is empty
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Interpolated value at x = 0.500 is y = 0.625
https://ideone.com/9V7dkZ
language:
Java (HotSpot 12)
created:
12 hours ago
visibility:
public

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