From f6750f035ce1275a6ec1511fec9fbae2e0cd935f Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Mon, 10 Nov 2025 23:58:17 +0800
Subject: [PATCH 1/2] Committed on or around 2025/11/10

---
 Miscellaneous/SOE/HappyNumber.java | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100644 Miscellaneous/SOE/HappyNumber.java

diff --git a/Miscellaneous/SOE/HappyNumber.java b/Miscellaneous/SOE/HappyNumber.java
new file mode 100644
index 0000000..154f990
--- /dev/null
+++ b/Miscellaneous/SOE/HappyNumber.java
@@ -0,0 +1,10 @@
+package SOE;
+
+public class HappyNumber {
+
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+
+	}
+
+}

From 0f4d0ad2aef284e0bd09628133e24b7afcf195ce Mon Sep 17 00:00:00 2001
From: Ceiling_roof <48134466+ResilientSpring@users.noreply.github.com>
Date: Tue, 11 Nov 2025 12:29:44 +0800
Subject: [PATCH 2/2] Committed on or around 2025/11/11

---
 Miscellaneous/SOE/HappyNumber.java | 43 +++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/Miscellaneous/SOE/HappyNumber.java b/Miscellaneous/SOE/HappyNumber.java
index 154f990..4507bc9 100644
--- a/Miscellaneous/SOE/HappyNumber.java
+++ b/Miscellaneous/SOE/HappyNumber.java
@@ -1,10 +1,47 @@
 package SOE;
 
+import java.util.HashSet;
+import java.util.Set;
+
 public class HappyNumber {
 
-	public static void main(String[] args) {
-		// TODO Auto-generated method stub
+    // 計算各位數平方和
+    static int next(int n) {
+        int sum = 0;
+        while (n > 0) {
+            int d = n % 10;
+            sum += d * d;
+            n /= 10;
+        }
+        return sum;
+    }
+
+    // 遞迴版 isHappy()
+    static boolean isHappy(int n) {
+        return isHappyHelper(n, new HashSet<>());
+    }
+
+    // 遞迴輔助函式：傳遞 seen 集合
+    private static boolean isHappyHelper(int n, Set<Integer> seen) {
+        if (n == 1)
+            return true; // 終止條件：快樂數
+        if (seen.contains(n))
+            return false; // 終止條件：進入循環
+
+        seen.add(n);
+        return isHappyHelper(next(n), seen);
+    }
 
-	}
+    // 測試
+    public static void main(String[] args) {
+        int[] nums = {1, 7, 19, 20, 25, 4};
 
+        for (int n : nums) {
+            System.out.printf("%d -> %s%n", n, isHappy(n));
+        }
+    }
 }
+
+// Source: https://chatgpt.com/c/69104fa3-4828-8321-ade1-f983f1f8c14c
+
+