leetcode 793

owen/leetcode/p793.py

@@ -0,0 +1,46 @@
+class Solution:
+    def preimageSizeFZF(self, k: int) -> int:
+        def Zeroes(x):
+            cnt = 0
+
+            while x > 0:
+                cnt += x // 5
+                x //= 5
+
+            return cnt
+
+
+        head = 0
+        tail = 10**10
+        while head < tail:
+            pivot = (head + tail )//2
+            if Zeroes(pivot) < k:
+                head = pivot + 1
+            else:
+                tail = pivot
+
+
+        if Zeroes(head) == k:
+            return 5
+        return 0
+
+
+# 10^9 =  
+# 1 * 2 * 3 * 4 * 5 * 6 * 7 * 8 * 9 * 10 * 11
+# 1 * (2*1) * 3 * (2*2) * (5*1) * (2*3) * 7 * (2*4) * 9 * (2*5) * 11
+# f(11) = 2 number is 11, 5 number is 2, 2*5 multiply is 2
+
+
+
+# f(0) = 0
+# f(1) = 0
+# f(2) = 0
+# f(3) = 0
+# f(4) = 0
+# f(5) = 1
+# f(6) = 1
+# f(7) = 1
+# f(8) = 1
+# f(9) = 1
+# f(10) = 2
+#1 * 2 * 3 * 4 * 5 * 6 * 7 * 8 * 9 * (5*2)