NumberTheory, Sequences, Statistics on double[], math and string property tests

README.md

@@ -20,7 +20,7 @@ Requires Java 25. Maven comes with the wrapper.
 src/main/java/io/github/diegourban/algorithms/
   datastructure/   array (shuffle), binarytree, linkedlist, queue, set, stack, vector
   io/              Reader: fast tokenising stdin reader for judge-style input
-  math/            Algebra (gcd, lcm, primes, factorisation), Combinatorics, Geometry, Numbers, Statistics
+  math/            NumberTheory (gcd, lcm, primes, factorisation), Sequences (Fibonacci), Combinatorics, Geometry, Measurement, Numbers, Statistics
   search/          BinarySearch.indexOf
   sorting/         Sorter interface: Insertion, Merge, Quick and Selection sort
   string/          StringUtils

src/main/java/io/github/diegourban/algorithms/math/Algebra.java → src/main/java/io/github/diegourban/algorithms/math/NumberTheory.java

@@ -1,11 +1,11 @@
 package io.github.diegourban.algorithms.math;
 
-import java.math.BigDecimal;
-import java.math.BigInteger;
-import java.math.RoundingMode;
 import java.util.*;
 
-public class Algebra {
+/**
+ * Number theory: greatest common divisor, least common multiple, primality and prime factorisation.
+ */
+public class NumberTheory {
 
     /**
      * Least common multiple (lcm) of two numbers.
@@ -137,85 +137,4 @@ private static void fillPrimeFactors(int number, Collection<Integer> factors) {
         }
     }
 
-    /**
-     * Calculates the nth Fibonacci number.
-     * Works with n <= 46
-     * <p>
-     * Solution: Using a bottom-up approach, starting with the 0th fibonacci number and iteratively computing subsequent numbers until we get to n.
-     * <p>
-     * Complexity: N time and O(1) space.
-     *
-     * @param n the nth number in the Fibonacci sequence to calculate
-     * @return the nth Fibonacci number
-     */
-    public static int fibonacci(int n) {
-        // edge cases:
-        if (n < 0) {
-            throw new IllegalArgumentException("Index was negative. No such thing as a negative index in a series.");
-        } else if (n == 0 || n == 1) {
-            return n;
-        }
-
-        // we'll be building the fibonacci series from the bottom up
-        // so we'll need to track the previous 2 numbers at each step
-        int prevPrev = 0;   // 0th fibonacci
-        int prev = 1;       // 1st fibonacci
-        int current = 0;    // Declare and initialize current
-
-        for (int i = 1; i < n; i++) {
-
-            // Iteration 1: current = 2nd fibonacci
-            // Iteration 2: current = 3rd fibonacci
-            // Iteration 3: current = 4th fibonacci
-            // To get nth fibonacci ... do n-1 iterations.
-            current = prev + prevPrev;
-            prevPrev = prev;
-            prev = current;
-        }
-
-        return current;
-    }
-
-    /**
-     * Calculates the nth Fibonacci number.
-     * Works with n <= 67
-     *
-     * @param n the nth number in the Fibonacci sequence to calculate
-     * @return the nth Fibonacci number
-     */
-    public static double fibonacciSimpleBinetFormula(int n) {
-        if (n == 0) {
-            return 0;
-        }
-        final double phi = (1 + Math.sqrt(5)) / 2;
-        final double sqrt5 = Math.sqrt(5);
-        return ((Math.pow(phi, n) - Math.pow(-phi, -n)) / sqrt5);
-    }
-
-    /**
-     * Calculates the nth Fibonacci number.
-     * Works with n <= 71
-     *
-     * @param n the nth number in the Fibonacci sequence to calculate
-     * @return the nth Fibonacci number
-     */
-    public static BigInteger fibonacciBinetFormula(int n) {
-        if (n == 0) {
-            return new BigInteger("0");
-        }
-        if (n == 1 || n == 2) {
-            return new BigInteger("1");
-        }
-        if (n == 3) {
-            return new BigInteger("2");
-        }
-
-        final double phi = (1 + Math.sqrt(5)) / 2;
-        BigDecimal sqrt5 = new BigDecimal(Math.sqrt(5));
-
-        BigDecimal pow = new BigDecimal(Math.pow(phi, n));
-        BigDecimal powInvrt = new BigDecimal(Math.pow(-phi, -n));
-        return pow.subtract(powInvrt).divide(sqrt5, RoundingMode.HALF_UP).toBigInteger();
-    }
-
 }

src/main/java/io/github/diegourban/algorithms/math/Sequences.java

@@ -0,0 +1,96 @@
+package io.github.diegourban.algorithms.math;
+
+import java.math.BigDecimal;
+import java.math.BigInteger;
+import java.math.RoundingMode;
+
+/**
+ * Number sequences.
+ */
+public class Sequences {
+
+    private Sequences() {
+    }
+
+    /**
+     * Calculates the nth Fibonacci number.
+     * Works with n <= 46
+     * <p>
+     * Solution: Using a bottom-up approach, starting with the 0th fibonacci number and iteratively computing subsequent numbers until we get to n.
+     * <p>
+     * Complexity: N time and O(1) space.
+     *
+     * @param n the nth number in the Fibonacci sequence to calculate
+     * @return the nth Fibonacci number
+     */
+    public static int fibonacci(int n) {
+        // edge cases:
+        if (n < 0) {
+            throw new IllegalArgumentException("Index was negative. No such thing as a negative index in a series.");
+        } else if (n == 0 || n == 1) {
+            return n;
+        }
+
+        // we'll be building the fibonacci series from the bottom up
+        // so we'll need to track the previous 2 numbers at each step
+        int prevPrev = 0;   // 0th fibonacci
+        int prev = 1;       // 1st fibonacci
+        int current = 0;    // Declare and initialize current
+
+        for (int i = 1; i < n; i++) {
+
+            // Iteration 1: current = 2nd fibonacci
+            // Iteration 2: current = 3rd fibonacci
+            // Iteration 3: current = 4th fibonacci
+            // To get nth fibonacci ... do n-1 iterations.
+            current = prev + prevPrev;
+            prevPrev = prev;
+            prev = current;
+        }
+
+        return current;
+    }
+
+    /**
+     * Calculates the nth Fibonacci number.
+     * Works with n <= 67
+     *
+     * @param n the nth number in the Fibonacci sequence to calculate
+     * @return the nth Fibonacci number
+     */
+    public static double fibonacciSimpleBinetFormula(int n) {
+        if (n == 0) {
+            return 0;
+        }
+        final double phi = (1 + Math.sqrt(5)) / 2;
+        final double sqrt5 = Math.sqrt(5);
+        return ((Math.pow(phi, n) - Math.pow(-phi, -n)) / sqrt5);
+    }
+
+    /**
+     * Calculates the nth Fibonacci number.
+     * Works with n <= 71
+     *
+     * @param n the nth number in the Fibonacci sequence to calculate
+     * @return the nth Fibonacci number
+     */
+    public static BigInteger fibonacciBinetFormula(int n) {
+        if (n == 0) {
+            return new BigInteger("0");
+        }
+        if (n == 1 || n == 2) {
+            return new BigInteger("1");
+        }
+        if (n == 3) {
+            return new BigInteger("2");
+        }
+
+        final double phi = (1 + Math.sqrt(5)) / 2;
+        BigDecimal sqrt5 = BigDecimal.valueOf(Math.sqrt(5));
+
+        BigDecimal pow = BigDecimal.valueOf(Math.pow(phi, n));
+        BigDecimal powInvrt = BigDecimal.valueOf(Math.pow(-phi, -n));
+        return pow.subtract(powInvrt).divide(sqrt5, RoundingMode.HALF_UP).toBigInteger();
+    }
+
+}

src/main/java/io/github/diegourban/algorithms/math/Statistics.java

@@ -11,13 +11,13 @@ public class Statistics {
      * @param data
      * @return
      */
-    public static double mean(int[] data) {
+    public static double mean(double[] data) {
         if (data.length == 0) {
             return 0.0;
         }
 
         double sum = 0.0;
-        for (int value : data) {
+        for (double value : data) {
             sum += value;
         }
 
@@ -30,7 +30,7 @@ public static double mean(int[] data) {
      * @param data
      * @return
      */
-    public static double median(int[] data) {
+    public static double median(double[] data) {
         Arrays.sort(data);
 
         final int middle = data.length / 2;
@@ -48,8 +48,8 @@ public static double median(int[] data) {
      * @param data
      * @return
      */
-    public static int mode(int[] data) {
-        int maxValue = 0;
+    public static double mode(double[] data) {
+        double maxValue = 0;
         int maxCount = 0;
 
         for (int i = 0; i < data.length; ++i) {
@@ -74,11 +74,11 @@ public static int mode(int[] data) {
      * @param data
      * @return the Average Absolute Deviation from data
      */
-    public static double meanAbsoluteDeviation(int[] data) {
+    public static double meanAbsoluteDeviation(double[] data) {
         double mean = mean(data);
 
         double sum = 0;
-        for (int value : data) {
+        for (double value : data) {
             sum += Math.abs(value - mean);
         }