# LeetCode 1018. Binary Prefix Divisible By 5

## Description

https://leetcode.com/problems/binary-prefix-divisible-by-5/

Given an array `A` of `0`s and `1`s, consider `N_i`: the i-th subarray from `A` 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 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. `1 <= A.length <= 30000`
2. `A[i]` is `0` or `1`

## Explanation

Just build a binary string and see if its decimal number can be divisible by 5.

## Python Solution

``````class Solution:
def prefixesDivBy5(self, A: List[int]) -> List[bool]:
results = []

binary_str = ""
for num in A:
binary_str += str(num)

if int(binary_str, 2) % 5 == 0:
results.append(True)
else:
results.append(False)

return results``````
• Time Complexity: O(N).
• Space Complexity: O(N).