Mind palace

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67. Add Binary

Posted on Edited on In Disqus:
Symbols count in article: 854 Reading time ≈ 1 mins.

O(max(m, n)) time O(1) space

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class Solution {
public:
    string addBinary(string a, string b) {
        string res;
        for (int c = 0, i = a.length() - 1, j = b.length() - 1;
            i >= 0 || j >= 0 || c > 0;
            --i, --j) {
            int x = i < 0 ? 0 : (a[i] - '0');
            int y = j < 0 ? 0 : (b[j] - '0');
            int s = x + y + c;
            res += '0' + (s & 1);
            c = s >> 1;
        }
        return string(rbegin(res), rend(res));
    }
};
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class Solution {
public:
    string addBinary(string a, string b) {
        if (a.empty()) return b;
        if (b.empty()) return a;
        int c = 0;
        string res;
        while (!a.empty() || !b.empty() || c > 0) {
            int x = a.empty() ? 0 : (a.back() - '0');
            int y = b.empty() ? 0 : (b.back() - '0');
            if (!a.empty()) {
                a.pop_back();
            }
            if (!b.empty()) {
                b.pop_back();
            }
            int s = x + y + c;
            res += '0' + (s & 1);
            c = (s >> 1);
        }
        return string(rbegin(res), rend(res));
    }
};