// Time:  O(n)
// Space: O(n)

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        unordered_set<int> nums_set(nums.begin(), nums.end());
        return nums_set.size() != nums.size();
    }
};

// Time:  O(nlogn)
// Space: O(1)
class Solution2 {
public:
    bool containsDuplicate(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        return unique(nums.begin(), nums.end()) != nums.end();
    }
};