Leetcode - Add Binary

iteye_17352

于 2015-06-13 17:34:04 发布

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分类专栏： String

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本文介绍了如何将两个二进制字符串相加并返回结果，包括处理字符串长度不一致的情况，以及实现进位逻辑。

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Given two binary strings, return their sum (also a binary string).

For example,
a = "11"
b = "1"
Return "100".

    public String addBinary(String a, String b) {
        if (a == null && b == null) return null;
        if (a == null || a.length() == 0) return b;
        if (b == null || b.length() == 0) return a;
        
        if (a.length() > b.length())
            return addBinary(b, a);
        int i = a.length() - 1;
        int j = b.length() - 1;
        StringBuilder sum = new StringBuilder();
        int carry = 0, curr = 0;
        while (i >= 0 && j >= 0) {
            curr = a.charAt(i--) - '0' + b.charAt(j--) - '0' + carry;
            carry = curr >> 1;
            sum.append(curr >= 2 ? curr - 2 : curr);
        }
        while (j >= 0) {
            curr = b.charAt(j--) - '0' + carry;
            carry = curr >> 1;
            sum.append(curr >= 2 ? curr - 2 : curr);
        }
        if (carry > 0)
            sum.append(carry);
        return sum.reverse().toString();
    }