利用NSArrays实现集合的交集与并集操作-ImplementingSetOperationswithNSArrays:IntersectionandUnion

21  

Convert the NSArrays to NSSets, the standard set operations are available.

将nsarray转换为nsset，可以使用标准的set操作。

NSArray *a = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", @"5", nil];
NSArray *b = [NSArray arrayWithObjects:@"4", @"5", @"6", @"7", nil];

NSMutableSet *setA = [NSMutableSet setWithArray:a];
NSSet *setB = [NSSet setWithArray:b];
[setA intersectSet:setB];
NSLog(@"c: %@", [setA allObjects]);

NSLog output: c: (4, 5)

NSLog输出:c:(4,5)

[setA unionSet:setB];
NSLog(@"d: %@", [setA allObjects]);

NSLog output: d: (6, 4, 7, 5)

NSLog输出:d:(6,4,7,5)

15  

As others have suggested, you can easily do this with NSSet. However, this will not preserve ordering.

正如其他人所建议的，您可以轻松地使用NSSet实现这一点。然而，这并不能保持顺序。

If you want to preserve ordering and you can target OS X 10.7+, then you can use the new NSOrderedSet (and mutable subclass) to do the same thing.

如果您想保持排序，并且您可以针对OS X 10.7+，那么您可以使用新的NSOrderedSet(和mutablecsubclass)来做同样的事情。

6  

By using NSSet, as others have pointed out. For

正如其他人所指出的，通过使用NSSet。为

NSArray * a = [NSArray arrayWithObjects: ... ];
NSArray * b = [NSArray arratWithObjects: ... ];
NSMutableSet * set = [NSMutableSet setWithArray:a];
[set intersectSet:[NSSet setWithArray:b];
[set unionSet:[NSSet setWithArray:b];

This takes care of dupes but won't preserve order. You'd take the results in "set" and sort them back into an array. There's no native collection functionality that will do it all-- if you prefer to keep the order and worry about dupes separately, use NSMutableArray's -removeObjectsInArray: method, etc.

这可以解决问题，但不能维持秩序。您将在“set”中获取结果并将其排序到一个数组中。如果您更倾向于保持订单和对dupes的担心，则使用NSMutableArray的-removeObjectsInArray:方法，等等。

1  

(A ∩ B) ∪ B will always give you B, so this is a pretty bizarre thing to want to calculate. It's like saying "Give me the set of all cars that are colored green, combined with the set of all cars". That's going to give you the set of all cars.

(∩B)∪B将永远给你,这是一个很奇怪的事情要计算。这就像说“给我一套绿色的车，再加上所有的车”。它会给出所有汽车的集合。

0  

There is an NSSet class you can use to perform these operations.

有一个NSSet类可以用来执行这些操作。