Find Last Repeated Character in a string

Code

func findLastRepeatedCharacter(_ input: String) -> Character? {
    var charDict: [Character: Int] = [:]

    // Count the occurrence of each character
    for char in input {
        if let count = charDict[char] {
            charDict[char] = count + 1
        } else {
            charDict[char] = 1
        }
    }

    // Iterate through the characters in reverse order
    for char in input.reversed() {
        if let count = charDict[char], count > 1 {
            return char
        }
    }

    return nil
}

Example

// Example usage
let inputString = "Hello, playground"
if let lastRepeatedChar = findLastRepeatedCharacter(inputString) {
    print("The last repeated character is: \(lastRepeatedChar)")
} else {
    print("No repeated characters found.")
}

Output

The last repeated character is: o