[Leetcode]217. Contains Duplicate

1. problem : 

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

 

2. solution 1 :

public class Solution {
    public boolean containsDuplicate(int[] nums) {
        HashMap<Integer, Integer> hashMap = new HashMap<>();
        for (int i=0; i < nums.length;i++) {
            if (hashMap.containsKey(nums[i])) {
                return true;
            } else {
                hashMap.put(nums[i],i);
            }
        }
        return false;
    }
}

HashMap을 써서, 값이 들어있다면, true 반환,  없다면 추가, 루프가 정상적으로 끝난다면, false 반환