README.md

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;
    }
};