67. Add Binary

题目描述和难度

• 题目描述：

输入: a = "11", b = "1"
输出: "100"

输入: a = "1010", b = "1011"
输出: "10101"

• 题目难度：简单。
• 英文网址：67. Add Binary 。
• 中文网址：67. 二进制求和 。

思路分析

求解关键：

参考解答

参考解答1

Python 写法：

class Solution(object):
    def addBinary(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: str
        """
        res = ''
        # 分别表示两个数从后向前的索引，后对齐
        i = len(a) - 1
        j = len(b) - 1
        # 表示进位标志
        carry = 0
        while i >= 0 or j >= 0:
            s = carry
            if i >= 0:
                s += ord(a[i]) - ord('0')
                i -= 1
            if j >= 0:
                s += ord(b[j]) - ord('0')
                j -= 1

            res = str(s % 2) + res
            carry = s // 2
        if carry == 1:
            return '1' + res
        return res

参考解答2

Java 写法：

public class Solution {

    public String addBinary(String a, String b) {
        int aLen = a.length();
        int bLen = b.length();
        int maxLen = Math.max(aLen, bLen);

        StringBuilder sa = new StringBuilder(a).reverse();
        StringBuilder sb = new StringBuilder(b).reverse();
        while (sa.length() < maxLen) {
            sa.append("0");
        }
        while (sb.length() < maxLen) {
            sb.append("0");
        }
        StringBuilder res = new StringBuilder();
        int sum = 0;
        int num1;
        int num2;
        for (int i = 0; i < maxLen; i++) {
            num1 = sa.charAt(i) - '0';
            num2 = sb.charAt(i) - '0';
            if (sum + num1 + num2 > 1) {
                res.append(sum + num1 + num2 - 2);
                sum = 1;
            } else {
                res.append(sum + num1 + num2);
                sum = 0;
            }
        }
        if (sum == 1) {
            res.append("1");
        }
        return res.reverse().toString();
    }

    public static void main(String[] args) {
        String a = "1010";
        String b = "1011";
        Solution solution = new Solution();
        String addBinary = solution.addBinary(a, b);
        System.out.println(addBinary);
    }
}

Python 写法：

class Solution(object):
    def addBinary(self, a, b):
        """
        :type a: str
        :type b: str
        :rtype: str
        """
        alen = len(a)
        blen = len(b)
        maxlen = max(alen, blen)
        ra = list(reversed(a))
        rb = list(reversed(b))
        while len(ra) < maxlen:
            ra.append('0')
        while len(rb) < maxlen:
            rb.append('0')

        result = []
        s = 0
        zero = ord('0')
        for i in range(maxlen):
            num1 = ord(ra[i]) - zero
            num2 = ord(rb[i]) - zero
            if s + num1 + num2 > 1:
                result.append(str(s + num1 + num2 - 2))
                s = 1
            else:
                result.append(str(s + num1 + num2))
                s = 0
        if s == 1:
            result.append(str(1))
        return ''.join(list(reversed(result)))


if __name__ == '__main__':
    a = "11"
    b = "1"
    solution = Solution()
    result = solution.addBinary(a, b)
    print(result)

参考解答2

Python 写法：

class Solution:
    def addBinary(self, a, b):
        return bin(int(a, 2) + int(b, 2))[2:]


if __name__ == '__main__':
    a = "11"
    b = "1"
    solution = Solution()
    result = solution.addBinary(a, b)
    print(result)

    result1 = int(a, 2)
    result2 = int(b, 2)
    print(result1)
    print(result2)

    print(bin(result1 + result2))
    print(bin(result1 + result2)[2:])

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