single number easy

Array/SingleNumber.py

@@ -0,0 +1,43 @@
+"""
+Given a non-empty array of integers, every element appears twice except for one. Find that single one.
+
+Note:
+
+Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?
+
+Example 1:
+
+Input: [2,2,1]
+Output: 1
+Example 2:
+
+Input: [4,1,2,1,2]
+Output: 4
+
+
+给定一个非空数组，除了一个元素外，其余均出现两次。找出它。
+
+需要在线性时间内，且不用额外空间。
+
+用到了 missing number 的思路，利用异或的性质，相同的异或会抵消掉。
+
+直接在原数组上操作，用了 i 变量，一个变量都不用要怎么写？
+Discuss里也没找到相关的。
+
+测试地址：
+https://leetcode.com/problems/single-number/description/
+
+"""
+
+class Solution(object):
+    def singleNumber(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+
+        for i in range(1, len(nums)):
+            nums[i] = nums[i] ^ nums[i-1]
+
+        return nums[-1]
+