Merge branch 'master' into refactor/find_kth_number

Author: siriak

src/main/java/com/thealgorithms/backtracking/NQueens.java

@@ -36,13 +36,10 @@ public final class NQueens {
     private NQueens() {
     }
 
-    public static void main(String[] args) {
-        placeQueens(1);
-        placeQueens(2);
-        placeQueens(3);
-        placeQueens(4);
-        placeQueens(5);
-        placeQueens(6);
+    public static List<List<String>> getNQueensArrangements(int queens) {
+        List<List<String>> arrangements = new ArrayList<>();
+        getSolution(queens, arrangements, new int[queens], 0);
+        return arrangements;
     }
 
     public static void placeQueens(final int queens) {

src/main/java/com/thealgorithms/conversions/HexToOct.java

@@ -1,7 +1,5 @@
 package com.thealgorithms.conversions;
 
-import java.util.Scanner;
-
 /**
  * Converts any Hexadecimal Number to Octal
  *
@@ -12,64 +10,53 @@ private HexToOct() {
     }
 
     /**
-     * This method converts a Hexadecimal number to a decimal number
+     * Converts a Hexadecimal number to a Decimal number.
      *
-     * @param s The Hexadecimal Number
-     * @return The Decimal number
+     * @param hex The Hexadecimal number as a String.
+     * @return The Decimal equivalent as an integer.
      */
-    public static int hex2decimal(String s) {
-        String str = "0123456789ABCDEF";
-        s = s.toUpperCase();
-        int val = 0;
-        for (int i = 0; i < s.length(); i++) {
-            char a = s.charAt(i);
-            int n = str.indexOf(a);
-            val = 16 * val + n;
+    public static int hexToDecimal(String hex) {
+        String hexDigits = "0123456789ABCDEF";
+        hex = hex.toUpperCase();
+        int decimalValue = 0;
+
+        for (int i = 0; i < hex.length(); i++) {
+            char hexChar = hex.charAt(i);
+            int digitValue = hexDigits.indexOf(hexChar);
+            decimalValue = 16 * decimalValue + digitValue;
         }
-        return val;
+
+        return decimalValue;
     }
 
     /**
-     * This method converts a Decimal number to a octal number
+     * Converts a Decimal number to an Octal number.
      *
-     * @param q The Decimal Number
-     * @return The Octal number
+     * @param decimal The Decimal number as an integer.
+     * @return The Octal equivalent as an integer.
      */
-    public static int decimal2octal(int q) {
-        int now;
-        int i = 1;
-        int octnum = 0;
-        while (q > 0) {
-            now = q % 8;
-            octnum = (now * (int) (Math.pow(10, i))) + octnum;
-            q /= 8;
-            i++;
+    public static int decimalToOctal(int decimal) {
+        int octalValue = 0;
+        int placeValue = 1;
+
+        while (decimal > 0) {
+            int remainder = decimal % 8;
+            octalValue += remainder * placeValue;
+            decimal /= 8;
+            placeValue *= 10;
         }
-        octnum /= 10;
-        return octnum;
+
+        return octalValue;
     }
 
     /**
-     * Main method that gets the hex input from user and converts it into octal.
+     * Converts a Hexadecimal number to an Octal number.
      *
-     * @param args arguments
+     * @param hex The Hexadecimal number as a String.
+     * @return The Octal equivalent as an integer.
      */
-    public static void main(String[] args) {
-        String hexadecnum;
-        int decnum;
-        int octalnum;
-        Scanner scan = new Scanner(System.in);
-
-        System.out.print("Enter Hexadecimal Number : ");
-        hexadecnum = scan.nextLine();
-
-        // first convert hexadecimal to decimal
-        decnum = hex2decimal(hexadecnum); // Pass the string to the hex2decimal function and get the decimal form in
-        // variable decnum
-
-        // convert decimal to octal
-        octalnum = decimal2octal(decnum);
-        System.out.println("Number in octal: " + octalnum);
-        scan.close();
+    public static int hexToOctal(String hex) {
+        int decimalValue = hexToDecimal(hex);
+        return decimalToOctal(decimalValue);
     }
 }

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

@@ -1,7 +1,5 @@
 package com.thealgorithms.maths;
 
-import java.util.Scanner;
-
 /*
  * @author Ojasva Jain
  * Determinant of a Matrix Wikipedia link: https://en.wikipedia.org/wiki/Determinant
@@ -10,8 +8,13 @@ public final class DeterminantOfMatrix {
     private DeterminantOfMatrix() {
     }
 
-    // Determinant calculator
-    //@return determinant of the input matrix
+    /**
+     * Calculates the determinant of a given matrix.
+     *
+     * @param a the input matrix
+     * @param n the size of the matrix
+     * @return the determinant of the matrix
+     */
     static int determinant(int[][] a, int n) {
         int det = 0;
         int sign = 1;
@@ -41,21 +44,4 @@ static int determinant(int[][] a, int n) {
         }
         return det;
     }
-
-    // Driver Method
-    public static void main(String[] args) {
-        Scanner in = new Scanner(System.in);
-        // Input Matrix
-        System.out.println("Enter matrix size (Square matrix only)");
-        int n = in.nextInt();
-        System.out.println("Enter matrix");
-        int[][] a = new int[n][n];
-        for (int i = 0; i < n; i++) {
-            for (int j = 0; j < n; j++) {
-                a[i][j] = in.nextInt();
-            }
-        }
-        System.out.println(determinant(a, n));
-        in.close();
-    }
 }

src/test/java/com/thealgorithms/backtracking/NQueensTest.java

@@ -0,0 +1,48 @@
+package com.thealgorithms.backtracking;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+public class NQueensTest {
+
+    @Test
+    public void testNQueens1() {
+        List<List<String>> expected = Arrays.asList(Arrays.asList("Q"));
+        assertEquals(expected, NQueens.getNQueensArrangements(1));
+    }
+
+    @Test
+    public void testNQueens2() {
+        List<List<String>> expected = new ArrayList<>(); // No solution exists
+        assertEquals(expected, NQueens.getNQueensArrangements(2));
+    }
+
+    @Test
+    public void testNQueens3() {
+        List<List<String>> expected = new ArrayList<>(); // No solution exists
+        assertEquals(expected, NQueens.getNQueensArrangements(3));
+    }
+
+    @Test
+    public void testNQueens4() {
+        List<List<String>> expected = Arrays.asList(Arrays.asList(".Q..", "...Q", "Q...", "..Q."), Arrays.asList("..Q.", "Q...", "...Q", ".Q.."));
+        assertEquals(expected, NQueens.getNQueensArrangements(4));
+    }
+
+    @Test
+    public void testNQueens5() {
+        // Only the number of solutions is tested for larger N due to the complexity of checking each board configuration
+        List<List<String>> result = NQueens.getNQueensArrangements(5);
+        assertEquals(10, result.size()); // 5x5 board has 10 solutions
+    }
+
+    @Test
+    public void testNQueens6() {
+        List<List<String>> result = NQueens.getNQueensArrangements(6);
+        assertEquals(4, result.size()); // 6x6 board has 4 solutions
+    }
+}

src/test/java/com/thealgorithms/conversions/HexToOctTest.java

@@ -5,10 +5,29 @@
 import org.junit.jupiter.api.Test;
 
 public class HexToOctTest {
+    @Test
+    public void testHexToDecimal() {
+        assertEquals(255, HexToOct.hexToDecimal("FF"));
+        assertEquals(16, HexToOct.hexToDecimal("10"));
+        assertEquals(0, HexToOct.hexToDecimal("0"));
+        assertEquals(4095, HexToOct.hexToDecimal("FFF"));
+    }
+
+    @Test
+    public void testDecimalToOctal() {
+        assertEquals(110, HexToOct.decimalToOctal(HexToOct.hexToDecimal("48")));
+        assertEquals(255, HexToOct.decimalToOctal(HexToOct.hexToDecimal("AD")));
+        assertEquals(377, HexToOct.decimalToOctal(255));
+        assertEquals(20, HexToOct.decimalToOctal(16));
+        assertEquals(0, HexToOct.decimalToOctal(0));
+        assertEquals(7777, HexToOct.decimalToOctal(4095));
+    }
 
     @Test
-    public void testHexToOct() {
-        assertEquals(110, HexToOct.decimal2octal(HexToOct.hex2decimal("48")));
-        assertEquals(255, HexToOct.decimal2octal(HexToOct.hex2decimal("AD")));
+    public void testHexToOctal() {
+        assertEquals(377, HexToOct.hexToOctal("FF"));
+        assertEquals(20, HexToOct.hexToOctal("10"));
+        assertEquals(0, HexToOct.hexToOctal("0"));
+        assertEquals(7777, HexToOct.hexToOctal("FFF"));
     }
 }

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

@@ -0,0 +1,50 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class DeterminantOfMatrixTest {
+
+    @Test
+    public void testDeterminant2x2Matrix() {
+        int[][] matrix = {{1, 2}, {3, 4}};
+        int expected = -2;
+        assertEquals(expected, DeterminantOfMatrix.determinant(matrix, 2));
+    }
+
+    @Test
+    public void testDeterminant3x3Matrix() {
+        int[][] matrix = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
+        int expected = 0;
+        assertEquals(expected, DeterminantOfMatrix.determinant(matrix, 3));
+    }
+
+    @Test
+    public void testDeterminant3x3MatrixNonZero() {
+        int[][] matrix = {{1, 2, 3}, {0, 1, 4}, {5, 6, 0}};
+        int expected = 1;
+        assertEquals(expected, DeterminantOfMatrix.determinant(matrix, 3));
+    }
+
+    @Test
+    public void testDeterminant1x1Matrix() {
+        int[][] matrix = {{7}};
+        int expected = 7;
+        assertEquals(expected, DeterminantOfMatrix.determinant(matrix, 1));
+    }
+
+    @Test
+    public void testDeterminant4x4Matrix() {
+        int[][] matrix = {{1, 0, 0, 1}, {0, 1, 0, 0}, {0, 0, 1, 0}, {1, 0, 0, 1}};
+        int expected = 0;
+        assertEquals(expected, DeterminantOfMatrix.determinant(matrix, 4));
+    }
+
+    @Test
+    public void testDeterminant4x4MatrixZero() {
+        int[][] matrix = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}, {13, 14, 15, 16}};
+        int expected = 0;
+        assertEquals(expected, DeterminantOfMatrix.determinant(matrix, 4));
+    }
+}