LC#202 checks if given number is Happy or not, in O(n) space

Author: NirmalSilwal

Leetcode/MustDoEasyList/HappyNumber202.java

@@ -0,0 +1,42 @@
+package MustDoEasyList;
+
+import java.util.HashMap;
+
+public class HappyNumber202 {
+
+	public static boolean isHappy(int n) {
+		if (n < 1)
+			return false;
+
+		// to put intermediate squares value
+		HashMap<Integer, Boolean> map = new HashMap<>();
+		map.put(n, true);
+
+		while (n != 1) {
+			n = getSquareDigits(n);
+
+			if (!map.containsKey(n)) {
+				map.put(n, true);
+			} else {
+				return false;
+			}
+		}
+
+		return n == 1 ? true : false;
+	}
+
+	private static int getSquareDigits(int n) {
+		int ans = 0;
+		while (n != 0) {
+			int rem = n % 10;
+			ans += rem * rem;
+			n /= 10;
+		}
+		return ans;
+	}
+
+	public static void main(String[] args) {
+		System.out.println(isHappy(19));
+		System.out.println(isHappy(2));
+	}
+}