217

217. Contains Duplicate (Easy)

Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.

 

Example 1:

Input: nums = [1,2,3,1]
Output: true

Example 2:

Input: nums = [1,2,3,4]
Output: false

Example 3:

Input: nums = [1,1,1,3,3,4,3,2,4,2]
Output: true

 

Constraints:

• 1 <= nums.length <= 105
• -109 <= nums[i] <= 109

Companies:
Apple, Amazon, Adobe, Microsoft

Related Topics:
Array, Hash Table

Similar Questions:

• Contains Duplicate II (Easy)
• Contains Duplicate III (Medium)

Solution 1.

// OJ: https://leetcode.com/problems/contains-duplicate/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(N)
class Solution {
public:
    bool containsDuplicate(vector<int>& A) {
        unordered_set<int> s(begin(A), end(A));
        return s.size() != A.size();
    }
};

Solution 2.

// OJ: https://leetcode.com/problems/contains-duplicate/
// Author: github.com/lzl124631x
// Time: O(NlogN)
// Space: O(1)
class Solution {
public:
    bool containsDuplicate(vector<int>& A) {
        sort(begin(A), end(A));
        for (int i = 1; i < A.size(); ++i) {
            if (A[i] == A[i - 1]) return true;
        }
        return false;
    }
};