Swap keys for values in a dictionary?
I have a dictionary in Swift that looks like this:
[
0: "82",
1: "12",
2: "3",
3: "42"
// Etc.
]
And let's say I want to swap keys for values 82 and 3, so the new dictionary looks like this:
[
0: "3",
1: "12",
2: "82",
3: "42"
// Etc.
]
How should I do it? (I didn’t find any hints and have no idea how to do this, so I don’t have the code I tried with this)
EDIT:
I just did this:
var first_key = 0
var second_key = 2
var first_value = dict[first_key]!
var second_value = dict[second_key]!
dict[first_key] = second_value
dict[second_key] = first_value
+3
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4 answers
The basic idea is to create a temporary variable to store one of the values as they are exchanged.
let tmp = dict[0]
dict[0] = dict[2]
dict[2] = tmp
Or you can use the global swap function for this (which does the same internally).
var dict = [
0: "82",
1: "12",
2: "3",
3: "42"
]
swap(&dict[0], &dict[2])
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You can do something like this by simply changing the values,
var dict = [
0: "82",
1: "12",
2: "3",
3: "42"
// Etc.
]
if let value = dict[key], let existingValue = dict[newKey] {
dict[key] = existingValue
dict[newKey] = value
}
The dict value is now new, with the values you wanted. Or you can also add a category to the dictionary, for example
extension Dictionary {
mutating func swap(key1: Key, key2: Key) {
if let value = self[key1], let existingValue = self[key2] {
self[key1] = existingValue
self[key2] = value
}
}
}
dict.swap(0, key2: 2)
print(dict)
Note, you don't really need to pass a pointer.
+2
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var random = ["LAX":"Los Angeles", "JFK":"New York"]
func flip <T, U>(_ dictionary: Dictionary<U, T>) -> Dictionary<T, U> {
let arrayOfValues: [T] = Array(dictionary.values)
let arrayOfKeys: [U] = Array(dictionary.keys)
var newDictionary: [T: U] = [:]
for i in 0...arrayOfValues.count-1 {
newDictionary[arrayOfValues[i]] = arrayOfKeys[i]
}
return newDictionary
}
flip(random) // You will get ["Los Angeles": "LAX", "New York": "JFK"]
0
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