problem
solution
option 1 - sorting
1  | class Solution {  | 
option 2 - hash table
1  | class Solution {  | 
analysis
- option 1
- time complexity 
O(n) - space complexity 
O(1) 
 - time complexity 
 - option 2
- time complexity 
O(n) - space complexity 
O(1) 
 - time complexity 
 
1  | class Solution {  | 
1  | class Solution {  | 
O(n)O(1)O(n)O(1)