OC - NSSet (set)

The difference from Array
The way of storage in memory is discontinuous
It is more efficient when searching for elements because hash is used. For example, to find an element set, it can be found directly through the hash algorithm.And Array needs to be traversed
to find the intersection and union

NSSet

Initialization

 NSSet*set = [[NSSet alloc]initWithObjects:@"a",@"b",nil];NSSet*set2 = [set2 setWithArray]

Check

if([set containsObject:@"a"])NSLog(@"YES");

Intersection

//set(a,b,c).set2(a,s,d,)if([set intersectsSet:set2])NSLog(@"YES");//Seek if there are the same elements[set intersectSet:set2];NSLog(@"%@",set);//a

Union

//set(a,b,c).set2(a,s,d,)
[set unionSet:set2];//The common ones in set2 and se1 will be added to the set.re
NSLog(@“%@”,set);//a,b,c,s,d

Seek complement

//set(a,b,c).set2(a,s,d,)
[set minusSet:set2];
NSLog(@“%@”,set);//b,c

NSMutableSet

NSMutableSet*mset = [[NSMutableSet alloc]initWithCapacity:0];[set addObject:@"a"];