Title Link: https://leetcode.com/problems/happy-number/
Topic:
Write an algorithm to determine if a number is "happy".
A happy number is a number defined by the following process:starting with any positive integer and replace the number by the Sum of the squares of its digits, and repeat the process until the number equals 1 (where it would stay), or it loops Endl essly in a cycle which does not include 1. Those numbers for which this process ends in 1 is happy numbers.
Example: is a happy number
- 12 + 92 = 82
- 82 + 22 = 68
- 62 + 82 = 100
- 12 + 02 + 02 = 1
Ideas:
If 4 or itself appears in the result of the calculation, it is not a happy number.
Algorithm:
[Java]View PlainCopy
- public   boolean ishappy ( int n) {
- char c[] = String.valueof (n). ToCharArray ();
- int  SUM =  Span class= "number" style= "margin:0px; padding:0px; Border:none; Color:rgb (192,0,0); Background-color:inherit ">0 ;  
- for ( char t : c) {
- int x = Integer.parseint (string.valueof (t));
- sum + = x * x;
- }
- if (sum == ) Span class= "number" style= "margin:0px; padding:0px; Border:none; Color:rgb (192,0,0); Background-color:inherit ">1
- return   true ;  
- } else   if (sum == ) Span class= "number" style= "margin:0px; padding:0px; Border:none; Color:rgb (192,0,0); Background-color:inherit ">4 | | sum == n)
- return   false ;  
- else   if (ishappy (sum))
- return   true ;  
- return   false ;  
- }
"Leetcode" Happy number