【leetcode】1018. Binary Prefix Divisible By 5

题目如下：

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

解题思路：本题很简单，往左移位即可。每移动一位，如果当前位置的值是1，值需要加上1。

代码如下：

class Solution(object):
    def prefixesDivBy5(self, A):
        """
        :type A: List[int]
        :rtype: List[bool]
        """
        res = []
        val = 0
        for i in A:
            val = val << 1
            if i == 1:
                val += 1
            res.append(val % 5 == 0)
        return res