217 Contains Duplicate - Easy

Problem:

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.

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

Constraints:

• 1 <= nums.length <= 105
• -109 <= nums[i] <= 109

Problem Analysis:

• initialise a dictionary to keep track of each element
• if any integer count appears more than once, return true
• Time Complexity: O(n)

Solutions:

class Solution:
    def containsDuplicate(self, nums: List[int]) -> bool:
        count= {}
        for n in nums:
            count[n] = count.get(n, 0) + 1
            if count[n] > 1:
                return True
        return False

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