Add Binary

Add Binary

问题：

Given two binary strings, return their sum (also a binary string).

思路：

　　归并排序收尾工作

我的代码：

public class Solution {
    public String addBinary(String a, String b) {
        if(a == null)   return b;
        if(b == null)   return a;
        String s = "";
        int plus = 0;
        int i = a.length() - 1;
        int j = b.length() - 1;
        for(; i >= 0 && j >= 0; i--,j--)
        {
            int one = (int)(a.charAt(i) - '0');
            int two = (int)(b.charAt(j) - '0');
            int sum = one + two + plus;
            if(sum >= 2)
            {
                s = (sum - 2) + s;
                plus = 1;
            }
            else
            {
                s = sum + s;
                plus = 0;
            }
        }
        while(i >= 0)
        {
            int one = (int)(a.charAt(i) - '0');
            int sum = one + plus;
            if(sum >= 2)
            {
                s = (sum - 2) + s;
                plus = 1;
            }
            else
            {
                s = sum + s;
                plus = 0;
            }
            i--;
        }
        while(j >= 0)
        {
            int two = (int)(b.charAt(j) - '0');
            int sum = two + plus;
            if(sum >= 2)
            {
                s = (sum - 2) + s;
                plus = 1;
            }
            else
            {
                s = sum + s;
                plus = 0;
            }
            j--;
        }
        return plus == 0 ? s : 1 + s; 
    }
}

他人代码：

public class Solution {
    public String addBinary(String a, String b) {
        if(a.length() < b.length()){
            String tmp = a;
            a = b;
            b = tmp;
        }
        
        int pa = a.length()-1;
        int pb = b.length()-1;
        int carries = 0;
        String rst = "";
        
        while(pb >= 0){
            int sum = (int)(a.charAt(pa) - '0') + (int)(b.charAt(pb) - '0') + carries;
            rst = String.valueOf(sum % 2) + rst;
            carries = sum / 2;
            pa --;
            pb --;
        }
        
        while(pa >= 0){
            int sum = (int)(a.charAt(pa) - '0') + carries;
            rst = String.valueOf(sum % 2) + rst;
            carries = sum / 2;
            pa --;
        }       
        
        if (carries == 1)
            rst = "1" + rst;
        return rst;
    }
}

学习之处：

• 他人代码里面用了两个循环就解决问题了，代码更加简洁，而我的代码里面用了三个循环，代码段太长了，需要精简
• 进位的命名用carries更加专业一些
• char c 类型的'0' 想转化成int 的0 int num = (int)(c - '0')
• 这道题竟然花了好几遍才过