如何交换NSMutableDictionary键和值到位? [英] How to swap `NSMutableDictionary` key and values in place?

问题描述

我有一个NSMutableDictionary，我想交换值&键.即，在交换值之后，值变成了键，而与其交换的键变成了值.所有键和值都是唯一的.由于尺寸非常大，因此需要就地解决方案.另外，键和值是NSString对象

I have a NSMutableDictionary and I want to swap values & keys. i.e, after swapping values becomes keys and its corresponding keys with become values All keys and values are unique. Looking for an in place solution because size is very big . Also, the keys and values are NSString objects

推荐答案

NSMutableDictionary *d = [NSMutableDictionary dictionaryWithDictionary:@{
                             @"key1" : @"value1",
                             @"key2" : @"value2"}];

for (NSString *key in [d allKeys]) {
    d[d[key]] = key;
    [d removeObjectForKey:key];
}

NSLog(@"%@", d); // => { value1 : key1,
                 //      value2 : key2 }

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假设

• 唯一值(因为它们将成为键)
• 值符合NSCopying(与上面相同)
• 没有值等于任何键(否则冲突名称将在此过程中丢失)

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Assumptions

• unique values (as they will become keys)
• values conform to NSCopying (same as above)
• no value is equal to any key (otherwise colliding names will be lost in the process)

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