Add 483. Smallest Good Base

LeetCode/0483_Smallest_Good_Base.py

@@ -0,0 +1,33 @@
+import math
+
+class Solution(object):
+    def smallestGoodBase(self, n):
+        """
+        :type n: str
+        :rtype: str
+        """
+        n = int(n)
+
+        for length in range(64, 2, -1):
+            l = 2
+            r = int(math.sqrt(n) + 1)
+
+            def sum(mid):
+                res = 0
+                for i in range(length - 1, -1, -1):
+                    res += mid ** i
+                    if res > n:
+                        return res
+                return res
+
+            while l < r - 1:
+                mid = (l + r) // 2
+                if sum(mid) <= n:
+                    l = mid
+                else:
+                    r = mid
+
+            if sum(l) == n:
+                return str(l)
+
+        return str(n - 1)