[LeetCode] 存在重复元素【217】

问题: 给你一个整数数组nums，如果任一值在数组中出现至少两次，返回True；如果数组中每个元素互不相同，返回False

示例1

输入: nums = [1,2,3,1]

输出: True

示例2

输入: nums = [1,2,3,4]

输出: False

示例3

输入: nums = [1,1,1,3,3,4,3,2,4,2]

输出: True

Python3解题 

# 解法1:set去重,比较长度
def containsDuplicate(nums):
    len_set_nums = len(set(nums))
    if (len_set_nums != len(nums)):
        return True
    else:
        return False

# 解法2:排序,比较是否相等
def containsDuplicate(nums):
    nums.sort()
    for i in range(len(nums)-1):
        if nums[i+1] == nums[i]:
            return True
    return False

# 解法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