5 lines simple Java Solution

  • 13

    public class Solution {

    public boolean containsDuplicate(int[] nums) {
        HashSet<Integer> flag = new HashSet<Integer>();
        for(int i : nums) {
            if(!flag.add(i)) {
                return true;
        return false;


  • 1

    code to interface

    Set<Integer> flag = new HashSet<Integer>();

  • 0

    Hmm...this is interesting. I am quite new to programming and I did not know about what the 'code to interface' practice before. Can you help me understand a bit more?

  • -10

    The time : O(n^2);
    the space : O(n).
    So,you may improve it.

  • 3

    Time is O(n) man. Do your homework.

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