Add Binary

做一个二进制数字加法器

按照正常思路进行加法即可，设定一个进位变量carry，然后进行模拟

class Solution {
public:
    string addBinary(string longStr, string shortStr) {
        string res;
        if (longStr.size() < shortStr.size())
        {
            res = longStr;
            longStr = shortStr;
            shortStr = res;
        }
        res = longStr;
        int carry = 0, bit = 0;
        int i = shortStr.size() - 1, j = longStr.size() - 1;
        for (; i >= 0; i--, j--)
        {
            bit = shortStr[i] + longStr[j] + carry -'0' - '0';
            switch (bit)
            {
            case 0:
                carry = 0;
                break;
            case 1:
                res[j] = '1';
                carry = 0;
                break;
            case 2:
                res[j] = '0';
                carry = 1;
                break;
            case 3:
                res[j] = '1';
                carry = 1;
                break;
            default:
                break;
            }
        }
        while (carry != 0 && j>=0)
        {
            bit = longStr[j] + carry - '0';
            switch (bit)
            {
            case 1:
                res[j] = '1';
                carry = 0;
                break;
            case 2:
                res[j] = '0';
                carry = 1;
                j--;
                break;
            default:
                break;
            }
        }
        if (carry == 1)
        {
            res = "1" + res;
        }
        return res;
    }
};

在评论区看到一个简短的代码，我做了一些小优化，性能和以上代码一样都是6ms，但是很值得学习

class Solution
{
public:
    string addBinary(string a, string b)
    {
        string s = "";
        int c = 0, i = a.size() - 1, j = b.size() - 1;
        while (i >= 0 || j >= 0 || c == 1)
        {
            c += i >= 0 ? a[i--] - '0' : 0;
            c += j >= 0 ? b[j--] - '0' : 0;
            s = char((c & 1)+ '0') + s;
            c = c >> 1;
        }
        return s;
    }
};

来自为知笔记(Wiz)