Add Happy Numbers (#2839)

Co-authored-by: Louve Le Bronec <loane.le.bronec@eisti.fr>
Co-authored-by: Yang Libin <contact@yanglibin.info>
Co-authored-by: Yang Libin <szuyanglb@outlook.com>

src/main/java/com/thealgorithms/others/HappyNumbersSeq.java

@@ -0,0 +1,35 @@
+package com.thealgorithms.others;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Scanner;
+import java.util.Set;
+
+public class HappyNumbersSeq {
+    private static final Set<Integer> CYCLE_NUMS = new HashSet<>(Arrays.asList(4, 16, 20, 37, 58, 145));
+
+    public static void main(String[] args) {
+        Scanner in = new Scanner(System.in);
+        System.out.print("Enter number: ");
+        int n = in.nextInt();
+        while (n != 1 && !isSad(n)) {
+            System.out.print(n + " ");
+            n = sumSquares(n);
+        }
+        String res = n == 1 ? "1 Happy number" : "Sad number";
+        System.out.println(res);
+    }
+
+    private static int sumSquares(int n) {
+        int s = 0;
+        for (; n > 0; n /= 10) {
+            int r = n % 10;
+            s += r * r;
+        }
+        return s;
+    }
+
+    private static boolean isSad(int n) {
+        return CYCLE_NUMS.contains(n);
+    }
+}

src/main/java/com/thealgorithms/searches/LinearSearchThread.java

@@ -0,0 +1,65 @@
+package com.thealgorithms.searches;
+
+import java.util.Scanner;
+
+public class LinearSearchThread {
+    public static void main(String[] args) {
+        int[] list = new int[200];
+        for (int j = 0; j < list.length; j++) {
+            list[j] = (int) (Math.random() * 100);
+        }
+        for (int y : list) {
+            System.out.print(y + " ");
+        }
+        System.out.println();
+        System.out.print("Enter number to search for: ");
+        Scanner in = new Scanner(System.in);
+        int x = in.nextInt();
+        Searcher t = new Searcher(list, 0, 50, x);
+        Searcher t1 = new Searcher(list, 50, 100, x);
+        Searcher t2 = new Searcher(list, 100, 150, x);
+        Searcher t3 = new Searcher(list, 150, 200, x);
+        t.start();
+        t1.start();
+        t2.start();
+        t3.start();
+        try {
+            t.join();
+            t1.join();
+            t2.join();
+            t3.join();
+        } catch (InterruptedException e) {
+        }
+        boolean found = t.getResult() || t1.getResult() || t2.getResult() || t3.getResult();
+        System.out.println("Found = " + found);
+    }
+}
+
+class Searcher extends Thread {
+    private final int[] arr;
+    private final int left, right;
+    private final int x;
+    private boolean found;
+
+    Searcher(int[] arr, int left, int right, int x) {
+        this.arr = arr;
+        this.left = left;
+        this.right = right;
+        this.x = x;
+    }
+
+    @Override
+    public void run() {
+        int k = left;
+        found = false;
+        while (k < right && !found) {
+            if (arr[k++] == x) {
+                found = true;
+            }
+        }
+    }
+
+    boolean getResult() {
+        return found;
+    }
+}