Create find-the-duplicate-number.py

Author: kamyu104

Python/find-the-duplicate-number.py

@@ -0,0 +1,24 @@
+# Time: O(n)
+# Space: O(1)
+
+class Solution(object):
+ def findDuplicate(self, nums):
+ """
+ :type nums: List[int]
+ :rtype: int
+ """
+ duplicate = 0
+ # Mark the value as visited by negative.
+ for num in nums:
+ if nums[abs(num) - 1] > 0:
+ nums[abs(num) - 1] *= -1
+ else:
+ duplicate = abs(num)
+ break
+ # Rollback the value.
+ for num in nums:
+ if nums[abs(num) - 1] < 0:
+ nums[abs(num) - 1] *= -1
+ else:
+ break
+ return duplicate