LeetCode67. 二进制求和

题目

给定两个二进制字符串，返回他们的和（用二进制表示）。

输入为非空字符串且只包含数字 1 和 0。

示例 1:

输入: a = "11", b = "1"
输出: "100"

示例 2:

输入: a = "1010", b = "1011"
输出: "10101"

分析

有些类似于大数相加，处理好进位，之后字符串拼接就可以了。

代码

class Solution {
    public String addBinary(String a, String b) {
        a = new StringBuilder(a).reverse().toString();
        b = new StringBuilder(b).reverse().toString();
        String re = "";
        int i = 0;
        int j = 0;
        while ( i < a.length() && i < b.length()){
            int y = ((a.charAt(i)-'0') + (b.charAt(i)-'0') + j )% 2;
            j = ((a.charAt(i)-'0') + (b.charAt(i)-'0' + j )) / 2;
            re += y;
            i++;
        }

        while ( i < a.length()){
            re += ((a.charAt(i)-'0')  + j ) %2 ;
            j = ((a.charAt(i)-'0')  + j ) / 2;
            i++;
        }

        while ( i < b.length()){
            re += ((b.charAt(i)-'0')  + j ) %2 ;
            j = ((b.charAt(i)-'0')  + j ) / 2;
            i++;
        }

        if (j == 1)
            re += "1";


        return new StringBuilder(re).reverse().toString();
    }
}