[leetcode] there are duplicate elements [217]

problem :  Give you an array of integers nums, If any value appears in the array At least twice , return True; If each element in the array is different from each other , return False

Example 1

Input : nums = [1,2,3,1]

Output : True

Example 2

Input : nums = [1,2,3,4]

Output : False

Example 3

Input : nums = [1,1,1,3,3,4,3,2,4,2]

Output : True

Python3 Problem solving  

#  solution 1:set duplicate removal , Compare the length 
def containsDuplicate(nums):
    len_set_nums = len(set(nums))
    if (len_set_nums != len(nums)):
        return True
    else:
        return False

#  solution 2: Sort , Comparison is equal 
def containsDuplicate(nums):
    nums.sort()
    for i in range(len(nums)-1):
        if nums[i+1] == nums[i]:
            return True
    return False

#  solution 3
def containsDuplicate(nums):
    if len(nums) <= 1:
        return False
    hashset = set()
    for i in nums:
        if i in hashset:
            return True
        else:
            hashset.add(i)
    return False

containsDuplicate([1,2,3,1]) # True
containsDuplicate([1,2,3,4]) # False
containsDuplicate([1,1,1,3,3,4,3,2,4,2]) # True