[Lintcode two-sum]两数之和（python，双指针）

题目链接：http://www.lintcode.com/zh-cn/problem/two-sum/

给一个整数数组，找到两个数使得他们的和等于一个给定的数target。

备份一份，然后排序。搞两个指针分别从左从右开始扫描，每次判断这两个数相加是不是符合题意，如果小了，那就把左边的指针向右移，同理右指针。然后在备份的数组里找到位置。

 class Solution:
     """
     @param numbers : An array of Integer
     @param target : target = numbers[index1] + numbers[index2]
     @return : [index1 + 1, index2 + 1] (index1 < index2)
     """
     def twoSum(self, numbers, target):
         # write your code here
         tmp = []
         for i in numbers:
             tmp.append(i)
         numbers = sorted(numbers)
         a = 0
         b = len(numbers) - 1
         while True:
             if numbers[a] + numbers[b] == target:
                 break
             elif numbers[a] + numbers[b] < target:
                 a += 1
             elif numbers[a] + numbers[b] > target:
                 b -= 1
         reta = numbers[a]
         retb = numbers[b]
         a = -1
         b = -1
         for i in range(0, len(tmp)):
             if tmp[i] == reta and a == -1:
                 a = i
             elif tmp[i] == retb and b == -1:
                 b = i
         if a > b:
             a = a ^ b
             b = a ^ b
             a = a ^ b
         return [a+1, b+1]