1018. Binary Prefix Divisible By 5

Problem

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 <= 10^5

• nums[i] is either 0 or 1.

Solution (Java)

class Solution {
    public List<Boolean> prefixesDivBy5(int[] nums) {
        List<Boolean> result = new ArrayList<>(nums.length);
        int remainder = 0;
        for (int j : nums) {
            remainder = (j + (remainder << 1)) % 5;
            result.add(remainder == 0);
        }
        return result;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).