Arrays & Hashing · Easy

Contains Duplicate

O(N) · O(N)

Initialize Hash Map

Target is 2. We iterate through nums array and maintain a hash map of { value: index }.

Array Elements & Pointers
1
i=0
2
i=1
3
i=2
1
i=3
Live Variables & Invariants
target:2
i:0
current:-
complement:-
Step 1 / 9
11%
Solution Code
1
function containsDuplicate(nums: number[]): boolean {
2
  const seen = new Set<number>();
3
  for (const num of nums) {
4
    if (seen.has(num)) return true;
5
    seen.add(num);
6
  }
7
  return false;
8
}
LeetCode IDE Console

Test Cases

3 cases from Blind 75 & NeetCode 150

Ask for a hint whenever you get stuck.