feat: Add Neville's Algorithm (#6842)

* feat: Add Neville's algorithm for polynomial interpolation

* Update Neville.java

* style: Fix linter formatting issues.

* Handled Div by Zero Case

* Update NevilleTest.java

* Update Neville.java

* Update NevilleTest.java

* Update Neville.java

src/test/java/com/thealgorithms/maths/NevilleTest.java

@@ -0,0 +1,69 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+public class NevilleTest {
+
+    @Test
+    public void testInterpolateLinear() {
+        // Test with a simple linear function y = 2x + 1
+        // Points (0, 1) and (2, 5)
+        double[] x = {0, 2};
+        double[] y = {1, 5};
+        // We want to find y when x = 1, which should be 3
+        double target = 1;
+        double expected = 3.0;
+        assertEquals(expected, Neville.interpolate(x, y, target), 1e-9);
+    }
+
+    @Test
+    public void testInterpolateQuadratic() {
+        // Test with a quadratic function y = x^2
+        // Points (0, 0), (1, 1), (3, 9)
+        double[] x = {0, 1, 3};
+        double[] y = {0, 1, 9};
+        // We want to find y when x = 2, which should be 4
+        double target = 2;
+        double expected = 4.0;
+        assertEquals(expected, Neville.interpolate(x, y, target), 1e-9);
+    }
+
+    @Test
+    public void testInterpolateWithNegativeNumbers() {
+        // Test with y = x^2 - 2x + 1
+        // Points (-1, 4), (0, 1), (2, 1)
+        double[] x = {-1, 0, 2};
+        double[] y = {4, 1, 1};
+        // We want to find y when x = 1, which should be 0
+        double target = 1;
+        double expected = 0.0;
+        assertEquals(expected, Neville.interpolate(x, y, target), 1e-9);
+    }
+
+    @Test
+    public void testMismatchedArrayLengths() {
+        double[] x = {1, 2};
+        double[] y = {1};
+        double target = 1.5;
+        assertThrows(IllegalArgumentException.class, () -> Neville.interpolate(x, y, target));
+    }
+
+    @Test
+    public void testEmptyArrays() {
+        double[] x = {};
+        double[] y = {};
+        double target = 1;
+        assertThrows(IllegalArgumentException.class, () -> Neville.interpolate(x, y, target));
+    }
+
+    @Test
+    public void testDuplicateXCoordinates() {
+        double[] x = {1, 2, 1};
+        double[] y = {5, 8, 3};
+        double target = 1.5;
+        assertThrows(IllegalArgumentException.class, () -> Neville.interpolate(x, y, target));
+    }
+}