Contains Duplicate
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.
Constraints:
- 1 <= nums.length <= 10^5
- -10^9 <= nums[i] <= 10^9
Examples:
Input: [1,2,3,1]
Output: true
Explanation: The array contains duplicate elements (1 appears twice).
Input: [1,2,3,4]
Output: false
Explanation: The array does not contain any duplicate elements.
Input: [1,1,1,3,3,4,3,2,4,2]
Output: true
Explanation: The array contains duplicate elements (1, 3, and 2 appear multiple times).
Solutions
Hash Set
We use a hash set to store unique elements from the array. We iterate through the array, and for each element, we check if it already exists in the set. If it does, we return true, indicating that the array contains duplicates. If we finish iterating through the array without finding any duplicates, we return false.
class Solution {
public: bool containsDuplicate(vector<int>& nums) {
unordered_set<int> set;
for (int num : nums) {
if (set.find(num) != set.end()) return true;
set.insert(num);
}
return false;
}
}
;Follow-up:
How would you solve this problem if the array is too large to fit into memory?
