leetcode-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.

用哈希表，如果该元素已经存在于哈希表，说明重复。

public class Solution {    public boolean containsDuplicate(int[] nums) {        boolean flag=false;    HashMap<Integer, Integer> hm=new HashMap<Integer, Integer>();    for(int i=0;i<nums.length;i++)    {    if(!hm.containsKey(nums[i]))    hm.put(nums[i], 1);    else    {    flag=true;    break;    }    }    return flag;    }}