```
# Method 1 -- Apply hashtable O(n)
# hashNum = {}
# for i in nums:
# if i not in hashNum:
# hashNum[i] = 1
# else:
# return True
# return False
# Method 2 -- Sorting
# l = len(nums)
# if l < 2:
# return False
# nums.sort()
# for i in range(l-1):
# if nums[i] == nums[i+1]:
# return True
# return False
# Method 3 -- Set solution for python
numsSet = set(nums)
if len(nums) == len(numsSet):
return False
return True
```