I applied through Stack Overflow, and a recruiter contacted me with a 75-minute test on HackerRank. After passing the test, we scheduled a telephone technical interview with two engineers.

They asked me to solve some algorithms problems and then to implement a Stack. This was followed by several questions about atomic/nonatomic, nonnull id, and what happens if you add nil to an NSArray.

Create a method that finds if string A is a substring of string B without using the substring method of NSString.

Implement MyStack. (A lot of questions about multi-threading)

@protocol Stack

• (void)pushObject:(nonnull id)obj;
• (nonnull id)popObject; @property (nonatomic, assign) NSInteger count; @end

@interface MyStack : NSObject

@end

@implementation MyStack

@end