Brooke

一、題目

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

 

二、程式作法

public class Solution
{
    public bool ContainsDuplicate(int[] nums)
    {
        HashSet<int> set = new HashSet<int>();
        for (int i = 0; i < nums.Length; i++)
            if (!set.Contains(nums[i]))
                set.Add(nums[i]);
            else
                return true;
        return false;
    }
}

 

三、思路筆記

題目要判斷一陣列的元素值是否有出現兩次以上。

你可以排序後再來比對。而我則是利用 HashSet 來判斷。