Contains Duplicate

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        unordered_set<int> seen;
        for (int v : nums) {
            if (!seen.insert(v).second) return true;
        }
        return false;
    }
};

func containsDuplicate(nums []int) bool {
    seen := map[int]bool{}
    for _, v := range nums {
        if seen[v] {
            return true
        }
        seen[v] = true
    }
    return false
}

from typing import List

class Solution:
    def containsDuplicate(self, nums: List[int]) -> bool:
        seen = set()
        for v in nums:
            if v in seen:
                return True
            seen.add(v)
        return False

function containsDuplicate(nums) {
    const seen = new Set();
    for (const v of nums) {
        if (seen.has(v)) return true;
        seen.add(v);
    }
    return false;
}

class Solution {
    public boolean containsDuplicate(int[] nums) {
        Set<Integer> seen = new HashSet<>();
        for (int v : nums) {
            if (!seen.add(v)) return true;
        }
        return false;
    }
}

function containsDuplicate(nums: number[]): boolean {
    const seen = new Set<number>();
    for (const v of nums) {
        if (seen.has(v)) return true;
        seen.add(v);
    }
    return false;
}