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Contains Duplicate

Difficulty: Easy

Problem Description

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.

Key Insights

  • The problem requires checking for duplicate values in an array.
  • A hash table (or set) can efficiently track seen numbers.
  • The problem can be solved in a single pass through the array.

Space and Time Complexity

Time Complexity: O(n)
Space Complexity: O(n)

Solution

To determine if there are any duplicates in the array, we can utilize a set to keep track of the numbers we have seen as we iterate through the array. For each number, we check if it is already in the set:

  • If it is, we return true since we found a duplicate.
  • If it isn't, we add it to the set and continue. If we finish iterating through the array without finding any duplicates, we return false.

Code Solutions

def containsDuplicate(nums):
    seen = set()  # Create a set to track seen numbers
    for num in nums:  # Iterate through each number in the array
        if num in seen:  # Check if the number is already in the set
            return True  # Duplicate found
        seen.add(num)  # Add the number to the set if not seen
    return False  # No duplicates found
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