【LeetCode】217. Contains Duplicate

Difficulty:easy

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Description

https://leetcode.com/problems/contains-duplicate/

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

Intuition

Use HashSet.

 

Solution

    public boolean containsDuplicate(int[] nums) {
        if(nums==null || nums.length<=1)
            return false;
        HashSet<Integer> set = new HashSet<>();
        for(int i : nums){
            if(set.contains(i)){
                return true;
            }else{
                set.add(i);
            }
        }
        return false;
    }

　　

Complexity

Time complexity : O(n)

Space complexity : O(n)

 

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