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1018. Binary Prefix Divisible By 5

Easy

You are given a binary array nums (0-indexed).

We define xi as the number whose binary representation is the subarray nums[0..i] (from most-significant-bit to least-significant-bit).

For example, if nums = [1,0,1], then x0 = 1, x1 = 2, and x2 = 5. Return an array of booleans answer where answer[i] is true if xi is divisible by 5.

Example 1:

Input: nums = [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: nums = [1,1,1]
Output: [false,false,false]

Constraints:

  • 1 <= nums.length <= 105
  • nums[i] is either 0 or 1.

Solution

class Solution:
    def prefixesDivBy5(self, nums: List[int]) -> List[bool]:
        res = []
        acc = 0

        for num in nums:
            acc = (2 * acc + num) % 5
            res.append(acc == 0)

        return res