(leetcode)Add Binary

class Solution {
public:
    string addBinary(string a, string b) {
        int car = 0;
        int cur_a = a.length()-1;
        int cur_b = b.length()-1;
        int num =0;
        string ret = "";
        while(cur_a>=0 && cur_b>=0)
        {
            int toa = 0;
            if(cur_a >= 0)
            {
                toa = char2int(a[cur_a--]);
            }
            
            int tob = 0;
            if(cur_b >= 0)
            {
                tob = char2int(b[cur_b--]);
            }
            
            num =car + toa + tob;
            num = num % 2;
            
            ret = ret + (char)num + (char)car;
            
            car =num / 2;
            
            
        }
        while(cur_a >=0)
        {
            int toa;
            toa = char2int(a[cur_a]);

            num =car + toa;
            num = num % 2;
            
            ret = ret + (char)num + (char)car;
            
            car =num / 2;
            
        }
        while(cur_b >= 0)
        {
            int tob;
            tob = char2int(b[cur_b]);

            num =car + tob;
            num = num % 2;
            
            ret = ret + (char)num + (char)car;
            
            car =num / 2;
        }
        
        return ret;
        
    }
 
    int char2int(char c)
    {
        return c-'0';
    }
    
    char int2char(bool b)
    {
        if(b)
        {
            return '1';
        }
        return '0';
    }
};

　以上方法Memory Limit Exceeded

修改后方法如下：

class Solution {
public:
    string addBinary(string a, string b) {
        int car = 0;
        int cur_a = a.length()-1;
        int cur_b = b.length()-1;
        int num =0;
        string ret;
        int toa = 0;
        int tob = 0;
        while(cur_a>=0 && cur_b>=0)
        {

            if(cur_a >= 0)
            {
                toa = char2int(a[cur_a--]);
            }


            if(cur_b >= 0)
            {
                tob = char2int(b[cur_b--]);
            }

            num =car + toa + tob;
            car =num / 2;
            num = num % 2;
			ret.insert(ret.begin(),int2char(num));
           /* ret = ret + int2char(num);*/


        }
        while(cur_a >=0)
        {
            toa = char2int(a[cur_a]);
            num =car + toa;
            car =num / 2;
            num = num % 2;
			ret.insert(ret.begin(),int2char(num));
            /*ret = ret + int2char(num);*/
			cur_a--;

        }
        while(cur_b >= 0)
        {
            tob = char2int(b[cur_b]);

            num =car + tob;
            car =num / 2;
            num = num % 2;
			ret.insert(ret.begin(),int2char(num));
            /*ret = ret + int2char(num) ;*/
			cur_b--;

        }

        if(car == 1) ret.insert(ret.begin(),'1'); /*ret += '1';*/
		return ret;

    }

    int char2int(char c)
    {
        return c-'0';
    }

    char int2char(int b)
    {
        if(b)
        {
            return '1';
        }
        return '0';
    }
};