1018. Binary Prefix Divisible By 5.java

1018. Binary Prefix Divisible By 5

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