14. Longest Common Prefix

class Solution {
    func longestCommonPrefix(_ strs: [String]) -> String {
        if strs.count == 1 {
            return strs[0]
        }
        var pref: String = ""
        let word = strs.first ?? ""
        for index in word.indices {
            let c = word[index]
            for j in 1..<strs.count {
                if strs[j].count == pref.count || c != strs[j][index] {
                    return pref
                }
            }
            pref.append(c)
        }
        return pref
    }
}