217 Contains Duplicate
Given an integer array nums, return true if any value appears at least twice in the array, and return false if every element is distinct.
class Solution {
public boolean containsDuplicate(int[] nums) {
HashSet<Integer> set=new HashSet<>();
for(int i=0;i<nums.length;++i){
if(set.contains(nums[i]))
return true;
set.add(nums[i]);
}
return false;
}
}