14. 最长公共前缀

14. 最长公共前缀

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class Solution {
    func longestCommonPrefix(_ strs: [String]) -> String {
        var ret = ""
        var stop = false
        let firstString = strs.first!
        guard !firstString.isEmpty else {
        	// 首个字符串是""
            return ""
        }
        var prefix = ""
        for maxLength in 1...firstString.count {
            prefix = String(firstString.prefix(maxLength))
            for str in strs {
                if !str.hasPrefix(prefix) {
                    ret = String(firstString.prefix(maxLength - 1))
                    stop = true
                    break
                }
            }
            if stop {
                break
            }
        }
        // 首个str整个都是前缀
        if !stop {
            ret = firstString
        }
        return ret
    }
}

运行结果