leetcode 67

简单的二进制加法。

string addBinary(string a, string b) {
        string res="";
        int m = a.size()-1;
        int n = b.size()-1;
        int carry=0;
        while(m>=0||n>=0)
        {
            int p=m>=0?a[m--]-'0':0; //若a数组遍历完则p赋值为0
            int q=n>=0?b[n--]-'0':0; //若b数组遍历完则q赋值为0
            carry+=(p+q);
            res=to_string(carry%2)+res;
            carry/=2;
        }
        return carry==1?"1"+res:res;
    }