← Arrays

Contains Duplicate

Easy
Python
def contains_duplicate(nums):
    return len(nums)!=len(set(nums))
Java
public boolean containsDuplicate(int[] nums){
    Set<Integer> s=new HashSet<>();
    for(int n:nums) if(!s.add(n)) return true;
    return false;
}

Key Insight

Python's set one-liner. Java's add() returns false on duplicate.

Python → Java Differences

  • Python set one-liner
  • s.add() returns false on dup
  • len comparison elegant
Python
def contains_duplicate(nums):
    return len(nums)!=len(set(nums))
Java
public boolean containsDuplicate(int[] nums){
    Set<Integer> s=new HashSet<>();
    for(int n:nums) if(!s.add(n)) return true;
    return false;
}

Algorithm Steps

1. Convert to set
2. Compare lengths
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