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Contain Duplicate

1. Description

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

2. Solution

In Java, HashSet can’t have duplicated values. After adding all the data to the set, compare the size and length in Set and Array. If not equal, it contains duplicates.

class Solution {
    public boolean containsDuplicate(int[] nums) {
        HashSet<Integer> set = new HashSet<Integer>();
        for(Integer val : nums) {
            set.add(val);
        }
        if(set.size() == nums.length) {
            return false;
        }
        return true;
    }
}