Preimage Size of Factorial Zeroes Function

heoh/leetcode-793.py

@@ -0,0 +1,25 @@
+def sub_g(x, p):
+    return x // (5**p)
+
+def g(x):
+    return sum(sub_g(x, i) for i in range(1, 15))
+
+def bs(lo, hi, x):
+    if hi >= lo:
+        mid = (hi + lo) // 2
+        if g(mid) == x:
+            return mid
+        elif g(mid) > x:
+            return bs(lo, mid-1, x)
+        else:
+            return bs(mid+1, hi, x)
+    else:
+        return -1
+
+class Solution:
+    def preimageSizeFZF(self, k: int) -> int:
+        result = bs(0, 10**10, k)
+        if result == -1:
+            return 0
+        else:
+            return 5