LeetCode 1018. Binary Prefix Divisible By 5

Description

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

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. 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).

Leave a Reply

Your email address will not be published.