【CodeWars】Ones and Zeros

1.题意

题目链接：https://www.codewars.com/kata/578553c3a1b8d5c40300037c

Given an array of ones and zeroes, convert the equivalent binary value to an integer.

Eg: [0, 0, 0, 1] is treated as 0001 which is the binary representation of 1.

Examples:

Testing: [0, 0, 0, 1] ==> 1
Testing: [0, 0, 1, 0] ==> 2
Testing: [0, 1, 0, 1] ==> 5
Testing: [1, 0, 0, 1] ==> 9
Testing: [0, 0, 1, 0] ==> 2
Testing: [0, 1, 1, 0] ==> 6
Testing: [1, 1, 1, 1] ==> 15
Testing: [1, 0, 1, 1] ==> 11
However, the arrays can have varying lengths, not just limited to 4.

题目的意思是给定一个整型数组，数组的每个元素只能取0或1，将数组所有元素按序组成的二进制串转换成十进制的数值

2. 代码

代码很简单，按照二进制计算的思路来写就行，假设返回的值是sum，初始化为0，从第一位开始，进行sum = sum * 2，然后再加上当前值，直到算完最后一位，我这里使用位运算，事实上和前面是一样的，只是更贴合二进制计算的本质

import java.util.List;

public class BinaryArrayToNumber {
    public static int ConvertBinaryArrayToInt(List<Integer> binary) {
        // Your Code
        int sum = 0;
        for(int i = 0;i < binary.size();i++){
         sum = sum << 1;
         sum = sum | binary.get(i);
        }
        return sum;
    }
}