TopkFrequentWords.swift

func topkFrequentWords(_ words: [String], _ k: Int) -> [String] {
    var hashMap = [String:Int]()
    for word in words {
        hashMap[word] = (hashMap[word] ?? 0) + 1
    }
    
    var keys = Array(hashMap.keys)
    keys.sort {
        let f1 = hashMap[$0] ?? 0 // get ob associated w/ key 1
        let f2 = hashMap[$1] ?? 0 // get ob associated w/ key 2
    
        if f1 == f2 {
            return $0 < $1
        } else {
            return f1 > f2
        }
    }
    
    print(keys)
    return keys
}

let vals = topkFrequentWords(["i", "love", "leetcode", "i", "love", "coding"], 2)
print(vals)