Add Two Binary

Question

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

Example

a = 11

b = 1

Return 100

Thoughts

没什么可说的，加个carry一个一个算过去

注意点

• 最后的carry如果是1也要加上去

Solution

class Solution:
    # @param {string} a a number
    # @param {string} b a number
    # @return {string} the result
    def addBinary(self, a, b):
        # Write your code here
        result = ""
        index1 = len(a) - 1
        index2 = len(b) - 1
        carry = 0
        while index1 >= 0 and index2 >= 0:
            curSum = int(a[index1]) + int(b[index2]) + carry
            if curSum < 2:
                carry = 0
                result = str(curSum) + result
            elif curSum == 2:
                carry = 1
                result = "0" + result
            elif curSum == 3:
                carry = 1
                result = "1" + result
            index1 -= 1
            index2 -= 1
        while index1 >= 0:
            curSum = int(a[index1]) + carry
            if curSum < 2:
                carry = 0
                result = str(curSum) + result
            else:
                carry = 1
                result = "0" + result
            index1 -= 1
        while index2 >= 0:
            curSum = int(b[index2]) + carry
            if curSum < 2:
                carry = 0
                result = str(curSum) + result
            else:
                carry = 1
                result = "0" + result
            index2 -= 1
        if carry == 1:
            result = str(carry) + result
        return result