Handled Div by Zero Case

Author: Keykyrios

src/main/java/com/thealgorithms/maths/Neville.java

@@ -1,5 +1,9 @@
+// Neville.java
 package com.thealgorithms.maths;
 
+import java.util.HashSet;
+import java.util.Set;
+
 /**
  * In numerical analysis, Neville's algorithm is an algorithm used for
  * polynomial interpolation. Given n+1 points, there is a unique polynomial
@@ -23,7 +27,7 @@ private Neville() {
      * @param target The x-coordinate at which to evaluate the polynomial.
      * @return The interpolated y-value at the target x-coordinate.
      * @throws IllegalArgumentException if the lengths of x and y arrays are different,
-     * or if the arrays are empty.
+     * if the arrays are empty, or if x-coordinates are not unique.
      */
     public static double interpolate(double[] x, double[] y, double target) {
         if (x.length != y.length) {
@@ -33,6 +37,13 @@ public static double interpolate(double[] x, double[] y, double target) {
             throw new IllegalArgumentException("Input arrays cannot be empty.");
         }
 
+        Set<Double> seenX = new HashSet<>();
+        for (double val : x) {
+            if (!seenX.add(val)) {
+                throw new IllegalArgumentException("Input x-coordinates must be unique.");
+            }
+        }
+
         int n = x.length;
         double[] p = new double[n];
         System.arraycopy(y, 0, p, 0, n); // Initialize p with y values