[Leetcode] 217. Contains Duplicate

題目: 217. Contains Duplicate

• Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

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

1. Hashmap

class Solution:
    def containsDuplicate(self, nums: List[int]) -> bool:

        dict_nums = {}

        for num in nums:
            if num in dict_nums:
                return True
            dict_nums[num] = dict_nums.get(num,0)+1
        return False

2. sort()

先做排序，將數值依照順序做排序

如果目前的和後一個數值一樣就回傳True

class Solution:
    def containsDuplicate(self, nums: List[int]) -> bool:

        nums.sort()

        for i in range(len(nums)-1):
            if nums[i] == nums[i+1]:
                return True

        return False