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Find Duplicates in Array

Given an array of integers numbers, determine whether the array contains any duplicate values. A duplicate is defined as any number that appears more than once in the array.

Input​

numbers: number[]: An array of integers

Examples​

Input: numbers = [5,7,1,3]
Output: false
Explanation: All elements in the array are unique.
Input: numbers = [10,7,0,0,9]
Output: true
Explanation: 0 appears more than once.
Input: numbers = [3,2,6,5,0,3,10,3,10,5]
Output: true
Explanation: 3,5, and 10 appears more than once.

Constraints​

  • 1 <= numbers.length <= 10,000
  • -1,000,000 <= numbers[i] <= 1,000,000

Solution​

TypeScript​

Click to expand
function containsDuplicate(numbers: number[]): boolean{
    const seenNumbers = new Set<number>();

    for(const number of numbers){
        if(seenNumbers.has(number)){
            return true;
        }
        seenNumbers.add(number);
    }
    return false;
}
Big O Analysis
  • Time Complexity: O(n) - We iterate through the array once, performing constant-time operations for adding and checking elements in the Set.
  • Space Complexity: O(n) - The Set requires additional space to store n element in the worst case when all elements are unique.

Java​

Click to expand
import java.util.HashSet;
import java.util.Set;

public class Solution {
    public boolean containsDuplicate(int[] numbers){
        Set<Integer> seenNumbers = HashSet.newHashSet(numbers.length);

        for(int number : numbers){
            if(!seenNumbers.add(number)){
                return true;
            }
        }

        return false;
    }
}
Big O Analysis
  • Time Complexity: O(n) - We iterate through the array once, performing constant-time operations for adding and checking elements in the Set.
  • Space Complexity: O(n) - The Set requires additional space to store n element in the worst case when all elements are unique.