import "sort"

func longestCommonPrefix(strs []string) string {
    if len(strs) == 0 {
        return ""
    }
    if len(strs) == 1 {
        return strs[0]
    }
    sort.Strings(strs)
    var i = 0
    var ans = ""
    var prefix = ""
    for i < len(strs[0]) {
        prefix += string([]rune(strs[0])[i])
        for _, str := range strs {
            if !hasPrefix(str, prefix) {
                return ans
            }
        }
        i++
        ans = prefix
    }
    return ans
}

func hasPrefix(s, p string) bool {
    if len(p) > len(s) {
        return false
    }
    var ss = []rune(s)
    var pp = []rune(p)
    for i := 0; i < len(pp); i++ {
        if pp[i] != ss[i] {
            return false
        }
    }
    return true
}