add-binary.py

# coding: utf-8

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
 flag = 0
 ret = ''
 a_i, b_i = len(a) - 1, len(b) - 1
 while (a_i >= 0) and (b_i >= 0):
 va, vb = int(a[a_i]), int(b[b_i])
 ret += str((va + vb + flag) % 2)
 flag = (va + vb + flag) / 2
 a_i -= 1
 b_i -= 1
 c_i = -1
 if (a_i >= 0) or (b_i >= 0):
 c = a if a_i >= 0 else b
 c_i = a_i if a_i >= 0 else b_i
 while c_i >= 0:
 ret += str((int(c[c_i]) + flag) % 2)
 flag = (int(c[c_i]) + flag) / 2
 c_i -= 1
 if flag:
 ret += str(flag)
 return ret[::-1] # Python没有提供直接反转字符串的函数，用切片凑合一下吧。

# easy: http://lintcode.com/zh-cn/problem/add-binary/