happy number

Author: jackzhenguo

Math/Math.Lib/HappyNumber.cs

@@ -0,0 +1,45 @@
+/* ==============================================================================
+ * 功能描述：PowerOfTwo  
+ * 创 建 者：gz
+ * 创建日期：2017/5/8 18:58:49
+ * ==============================================================================*/
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace Math.Lib
+{
+    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, replace the number by the sum of the squares of its digits, and 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 numbers.
+
+Example: 19 is a happy number
+
+1^2 + 9^2 = 82
+8^2 + 2^2 = 68
+6^2 + 8^2 = 100
+1^2 + 0^2 + 0^2 = 1
+public class HappyNumberSln {
+    public bool IsHappy(int n) {
+        int slow =n, fast = n;
+        do{
+            slow = getSum(slow);
+            fast = getSum(fast);
+            fast = getSum(fast);
+        }while(slow!=fast);
+        return slow==1;
+    }
+    
+    public int getSum(int n){
+        int sum=0;
+        int tmp = n;
+        while(tmp>0){
+            int i = tmp%10;
+            sum+=i*i;
+            tmp = tmp/10;
+        }
+        return sum;
+    }
+}
+}