LeetCode: Contains Duplicate (c++)

Given an array of integers, find if the array contains any duplicates.

Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

Example 1:

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

Example 2:

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

Example 3:

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

	// Solution1: brute force that works but exceeds time limits due to complexity of 0(n^2)
	bool containsDuplicate(vector & amp; nums) {
	for (unsigned int i = 0; i & lt; nums.size(); i++)
	{
	for (unsigned int j = i + 1; j & lt; nums.size(); j++)
	{
	if (nums[i] == nums[j])
	{
	return true;
	}
	}
	}
	return false;
	}
	// Solution 2: Complexity is reduced (Accepted Answer)
	bool containsDuplicate(vector & amp; nums) {
	// Prevent against bad input
	if (nums.size() == 0)
	{
	return false;
	}
	// Put the data in set
	std::set mSet(nums.begin(), nums.end());
	// Sets are unique, and thus if the size is
	// same as vector then there are no duplicates
	if (mSet.size() == nums.size())
	{
	return false;
	} else
	{
	return true;
	}
	}

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