◻️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

---

Solutions

Normal

Runtime 85 ms Memory 61.02 MB

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        std::sort(nums.begin(), nums.end());
        int a=nums[0];
        for(int i=1; i<nums.size(); i++){
            if(a==nums[i]){
                return true;
            }
            a=nums[i];
        }
        return false;
    }
};

Striver

Runtime 99 ms Memory 75.55 MB

// striver

class Solution {
public:
    bool containsDuplicate(vector<int>& nums) {
        unordered_set<int> set;
        for(int i=0; i<nums.size(); i++){
            set.insert(nums[i]);
        }
        if(set.size() < nums.size())
            return true;
        return false;
    }
};