the question answered above are definitely not optimized but easy built in function, I doubt thats what the interviewer want, if it's sorted array, it will be easy, we simply keep track of the current number, remove duplicate and move forward, but if it's not sorted, then I think a NSMutableDictionary would be efficient to perform a one time scan from begin to the end, so it's O(n) time and O(n) space.

Is it alright if we use NSOrderedSet? Or do they expect you to solve it without using the built-in components. Because with NSOrderedSet, it can be solved in 1 line.

func removeDuplicates(ray:inout[Int])->[Int]{ ray = Array(Set(ray)) return ray } removeDuplicates(ray: &ray) OR func removeD(ray:[Int])->[Int]{ var ans=[Int]() var djSet=Set() for item in ray{ if djSet.contains(item){ continue }else{ djSet.insert(item) ans.append(item) } } return ans } var a = [2,1,3,5,1,2,5] removeD(ray: a)

import Foundation func removeDuplicates(array: [Int]) -> [Int] { var set = Set() var result = Array() for number in array { if set.contains(number) { continue } set.insert(number) result.append(number) } return result } var initialArray = [2, 1, 3, 1, 2]; var finalArray = removeDuplicates(array: initialArray) print(finalArray) // [2, 1, 3]

private var dismissNotificationTask: DispatchWorkItem? dismissNotificationTask = DispatchWorkItem { print("Hello") } if let dTask = dismissNotificationTask { let delay = DispatchTime.now() + .seconds(8) DispatchQueue.main.asyncAfter(deadline: delay, execute: dTask) } dismissNotificationTask?.cancel()

I think Matteo's first solution is not correct. Because the question asked to keep the first occurrence, but solution 1 removed the first occurrence. Solution 2 is brilliant, btw.

NSArray *input = @[@2, @1, @3, @1, @2]; NSArray *output = @[@2, @1, @3]; NSMutableArray *result = [NSMutableArray array]; for (id element in input) { if ([result containsObject:element] == NO) { [result addObject:element]; } } NSCAssert([result isEqualTo:output], @"fail");

-(NSMutableArray*)arrayWithoutDuplicates:(NSArray*)array { NSMutableArray *resultArray = [[NSMutableArray alloc] init]; for (int i = 0; i < array.count; i++) { if ( [resultArray containsObject:array[i]] ) { NSLog(@"resultArray already has this object: %@", array[i]); } else [resultArray addObject:array[i]]; } return resultArray; }

Is the array sorted? If so, sounds similar to oj.leetcode.com/problems/remove-duplicates-from-sorted-array/

your new array=[[NSSet setWithArray:yourOldArray] allObjects];

Sorry, what was you response at the first question? Is banal, but in Objective-C there are different solution.. I write 2 solution very fast, but the second is exponential faster then the first one. //First solution (1 to 1) - (NSMutableArray *)removeDuplicateFromArray:(NSMutableArray *)arr { if([arr count] = 0 && pos < i) { [arr removeObjectAtIndex:i]; i--; } } return arr; } //Other solution - (NSMutableArray *)removeDuplicateInGroupFromArray:(NSMutableArray *)arr { if([arr count] < 2) return arr; for(int i=0; i<[arr count]-1; i++) { [arr removeObject:arr[i] inRange:NSMakeRange(i+1, [arr count]-i-1)]; } return arr; }