愛比的新手筆記

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

HashSet比List還快, 所以用HasSet

public bool ContainsDuplicate(int[] nums)
{
    HashSet<int> hs = new HashSet<int>();
    foreach (int i in nums)
    {
        if (hs.Contains(i)) return true;
        hs.Add(i);
    }
    return false;
}

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