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EasyLeetCode #217Arrays & Hashing

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.

Constraints
1 <= nums.length <= 10^5, -10^9 <= nums[i] <= 10^9
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Examples
Input: nums = [1,2,3,1]
Output: true
Input: nums = [1,2,3,4]
Output: false
Solution

Approach

Use a HashSet to track seen numbers. If a number is already in the set, return true. Otherwise, add it and continue.

def containsDuplicate(nums):
    return len(nums) != len(set(nums))
Complexity
Time:O(n)
Space:O(n)
Hints
  • 1.What data structure provides O(1) lookup and insertion?
  • 2.Consider using a Set
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