Single Number

Author: gavinfish

136 Single Number.py

@@ -0,0 +1,21 @@
+'''
+Given an 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?
+'''
+
+class Solution(object):
+    def singleNumber(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: int
+        """
+        result = nums[0]
+        for i in nums[1:]:
+            result ^= i
+        return result
+
+
+if __name__ == "__main__":
+    assert Solution().singleNumber([1, 2, 3, 4, 3, 2, 1]) == 4