Swift Tutorials

How to Swap Keys and Values in a Dictionary in Swift

How to Swap Keys and Values in a Dictionary in Swift ?

Answer

To swap keys and values in a dictionary in Swift, you can use a `for` loop to iterate through the original dictionary and add each key-value pair to a new dictionary with the key and value swapped. This allows you to create a new dictionary where the keys and values are swapped.

✐ Examples

1 Swapping Keys and Values in a Dictionary Using a `for` Loop

We can swap keys and values in a dictionary in Swift using a `for` loop. This example demonstrates how to declare and initialize a dictionary, use a `for` loop to swap the keys and values, and print the resulting dictionary.

For example,

We start by declaring and initializing a dictionary named originalDict with integer keys and string values.
We declare an empty dictionary named swappedDict to store the swapped key-value pairs.
We use a `for` loop to iterate through the original dictionary and add each key-value pair to the new dictionary with the key and value swapped.
We print the resulting dictionary.

Swift Program

var originalDict: [Int: String] = [
    1: "One",
    2: "Two",
    3: "Three"
]

// Declare an empty dictionary to store the swapped key-value pairs
var swappedDict: [String: Int] = [:]

// Use a for loop to swap the keys and values
for (key, value) in originalDict {
    swappedDict[value] = key
}

// Print the resulting dictionary
print("Swapped dictionary:")
for (key, value) in swappedDict {
    print("Key: \(key), Value: \(value)")
}

Output

Swapped dictionary:
Key: One, Value: 1
Key: Two, Value: 2
Key: Three, Value: 3

2 Swapping Keys and Values in a Dictionary with Duplicate Values

We can swap keys and values in a dictionary with duplicate values in Swift by checking for duplicates and handling them appropriately. This example demonstrates how to declare and initialize a dictionary with duplicate values, use a `for` loop to swap the keys and values while handling duplicates, and print the resulting dictionary.

For example,

We start by declaring and initializing a dictionary named originalDict with integer keys and string values, including duplicate values.
We declare an empty dictionary named swappedDict to store the swapped key-value pairs, with arrays as values to handle duplicates.
We use a `for` loop to iterate through the original dictionary, check for duplicate values, and add each key-value pair to the new dictionary with the key and value swapped.
We print the resulting dictionary.

Swift Program

var originalDict: [Int: String] = [
    1: "One",
    2: "Two",
    3: "One"
]

// Declare an empty dictionary to store the swapped key-value pairs
var swappedDict: [String: [Int]] = [:]

// Use a for loop to swap the keys and values
for (key, value) in originalDict {
    if swappedDict[value] == nil {
        swappedDict[value] = [Int]()
    }
    swappedDict[value]?.append(key)
}

// Print the resulting dictionary
print("Swapped dictionary:")
for (key, value) in swappedDict {
    print("Key: \(key), Values: \(value)")
}

Output

Swapped dictionary:
Key: One, Values: [1, 3]
Key: Two, Values: [2]

Summary

In this tutorial, we learned How to Swap Keys and Values in a Dictionary in Swift language with well detailed examples.

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How to Swap Keys and Values in a Dictionary in Swift