easy math ifelse

202. Happy Number
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Write an algorithm to determine if a number n is happy.

A happy number is a number defined by the following process:

Starting with any positive integer, replace the number by the sum of the squares of its digits.
Repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1.
Those numbers for which this process ends in 1 are happy.
Return true if n is a happy number, and false if not.

 

Example 1:

Input: n = 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
Example 2:

Input: n = 2
Output: false
 

Constraints:

1 <= n <= 231 - 1

Author: Gauranshgoel123

happy-number.java

@@ -0,0 +1,18 @@
+class Solution {
+    public boolean isHappy(int n) {
+        if(n==1 || n==7 || n==10 || n==100 ) return true;
+        if(n>1 && n<10) return false;
+        while(n!=1){
+            int sum=0;
+            while(n!=0){
+                int rem=n%10;
+                sum+=(rem*rem);
+                n=n/10;
+            }         
+            n=sum;
+            if(sum==1||sum==7) return true;
+            if(sum>1 && sum<10) return false;
+        }
+        return false;
+    }
+}