Check Duplicate

出处

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.

Solution

用一个哈希表检测即可

Complexity

时间复杂度 O(n)，空间复杂度 O(n)

Code

public class Solution {
    public boolean containsDuplicate(int[] nums) {
        if(nums==null || nums.length==0)
            return false;
 
        HashSet<Integer> set = new HashSet<Integer>();
        for(int i: nums){
            if(!set.add(i)){
                return true;
            }
        }
     
        return false;
    }
}