1018

1018. Binary Prefix Divisible By 5 (Easy)

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

Related Topics:
Array

Solution 1.

// OJ: https://leetcode.com/problems/binary-prefix-divisible-by-5/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(1)
class Solution {
public:
    vector<bool> prefixesDivBy5(vector<int>& A) {
        vector<bool> ans;
        int val = 0;
        for (int n : A) {
            val = ((val << 1) + n) % 5;
            ans.push_back(val == 0);
        }
        return ans;
    }
};