public class Solution {
public boolean containsDuplicate(int[] nums) {
if (nums.length ==0  nums.length == 1){
return false;
}
Arrays.sort(nums);
for (int i=0;i<nums.length1;i++){
if (nums[i] == nums[i+1]){
return true;
}
}
return false;
}
}
Java solution with sorting O(nlog(n)) time O(1) space

As time complexity is more sensitive, we prefer a faster solution but o(n) space complexity which can be done using an hashset
here is my c++ solution , of course it's simple , and everyone can come out with this idea
class Solution { unordered_set<int> check; public: bool containsDuplicate(vector<int>& nums) { if(nums.size() <= 1) return false; for(int i = 0; i < nums.size(); i++){ if(check.find(nums[i]) != check.end()) return true; check.insert(nums[i]); } return false; } };