Daily Coding Day One Sixty Two

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Oh beautiful, for spacious skies, for Amber waves of …

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Given a list of words, return the shortest unique prefix of each word. 
For example, given the list:

dog
cat
apple
apricot
fish
Return the list:

d
c
app
apr
f

I used a dictionary on this bad boy and am just keeping track of the count. Does not seem wildly efficient, and honestly I’m not sure I even understand the question but Wynaut:

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import Foundation

func prefix(_ words: [String]) -> [String] {
    // dict to keep count of preix to count
    var prefixCount = [String: Int]()
    
    // Add prefixes, nothing fancy. Grab chars, Add chars
    for word in words {
        var prefix = ""
        for char in word {
            prefix += String(char)
            prefixCount[prefix, default: 0] += 1
        }
    }
    
    // find the lowest number, in our case 1s
    var result = [String]()
    for word in words {
        var prefix = ""
        for char in word {
            prefix += String(char)
            if prefixCount[prefix] == 1 {
                result.append(prefix)
                break
            }
        }
    }
    
    return result
}

Given some input
let words = ["dog", "cat", "apple", "apricot", "fish"]
and calling
print(shortestUniquePrefixes(words))
would print
["d", "c", "app", "apr", "f"]