1018 Binary Prefix Divisible By 5.py

Author: rajeevranjancom

1018 Binary Prefix Divisible By 5.py

@@ -0,0 +1,52 @@
+#!/usr/bin/python3
+"""
+Given an array A of 0s and 1s, consider N_i: the i-th subarray from A[0] to A[i]
+interpreted as a binary number (from most-significant-bit to
+least-significant-bit.)
+
+Return a list of booleans answer, where answer[i] is true if and only if N_i is
+divisible by 5.
+
+Example 1:
+
+Input: [0,1,1]
+Output: [true,false,false]
+Explanation:
+The input numbers in binary are 0, 01, 011; which are 0, 1, and 3 in base-10.
+Only the first number is divisible by 5, so answer[0] is true.
+Example 2:
+
+Input: [1,1,1]
+Output: [false,false,false]
+Example 3:
+
+Input: [0,1,1,1,1,1]
+Output: [true,false,false,false,true,false]
+Example 4:
+
+Input: [1,1,1,0,1]
+Output: [false,false,false,false,false]
+
+Note:
+1 <= A.length <= 30000
+A[i] is 0 or 1
+"""
+from typing import List
+
+
+class Solution:
+    def prefixesDivBy5(self, A: List[int]) -> List[bool]:
+        """
+        brute force
+        """
+        cur = 0
+        ret = []
+        for a in A:
+            cur = (cur << 1) + a
+            cur %= 5
+            if cur == 0:
+                ret.append(True)
+            else:
+                ret.append(False)
+
+        return ret