Classic 150 Interview Questions P67 Add Binary

---

Timeline

Timeline

2025-11-25

init

Bit manipulation

---

Problem:

P67 Add Binary

https://leetcode.cn/problems/add-binary/description/?envType=study-plan-v2&envId=top-interview-150

Note the final carry

#include <string>
#include <algorithm>
using std::string;

class Solution {
    public:
	string addBinary(string a, string b)
	{
		int i = a.size() - 1, j = b.size() - 1;
		int carry = 0;
		int curr_a_bit, curr_b_bit, curr_sum;
		string res;
		while (i >= 0 || j >= 0) {
			if (i < 0) {
				curr_a_bit = 0;
			} else {
				curr_a_bit = a[i] - '0';
				i--;
			}
			if (j < 0) {
				curr_b_bit = 0;
			} else {
				curr_b_bit = b[j] - '0';
				j--;
			}

			curr_sum = carry + curr_a_bit + curr_b_bit;
			carry = curr_sum / 2;
			res.push_back('0' + curr_sum % 2);
		}
		if (carry == 1) {
			res.push_back('1');
		}
		std::reverse(res.begin(), res.end());
		return res;
	}
};
int main()
{
	Solution S;
	S.addBinary("11", "1");
}