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Description:
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 <= A.length <= 30000
- A[i] is 0 or 1
题意:给定一个数组A,仅包含0或1;定义N_i为以A[0],A[1],…A[i]表示的数,计算N_i是否能被5整除;
解法:我们知道能被5整除的数必定满足最后一位的数字为0或者5;所以我们只需要判断N_i的最后一位是否满足即可,即计算
是否满足条件即可;
Java
class Solution {
public List<Boolean> prefixesDivBy5(int[] A) {
List<Boolean> res = new ArrayList<>();
int num = 0;
for (int a: A) {
num = (num << 1) % 10 + a;
res.add(num == 0 || num == 5 ? true : false);
}
return res;
}
}