Create 56. 快乐数.md

Author: jasoncao11

56. 快乐数.md

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+***编写一个算法来判断一个数 n 是不是快乐数。***
+
+```
+输入：n = 19
+输出：true
+解释：
+12 + 92 = 82
+82 + 22 = 68
+62 + 82 = 100
+12 + 02 + 02 = 1
+```
+
+```
+def isHappy(self, n: int) -> bool:  
+    def get_next(number):
+        total_sum = 0
+        while number > 0:
+            number, digit = divmod(number, 10)
+            total_sum += digit ** 2
+        return total_sum
+
+    slow_runner = n
+    fast_runner = get_next(n)
+    while fast_runner != 1 and slow_runner != fast_runner:
+        slow_runner = get_next(slow_runner)
+        fast_runner = get_next(get_next(fast_runner))
+    return fast_runner == 1
+```