腾讯T2面试题

Question

编写一个函数来查找字符串数组中的最长公共前缀。如果不存在公共前缀，返回空字符串 ""。示例 1:
输入: ["flower","flow","flight"]
输出: "fl"示例 2:
输入: ["dog","racecar","car"]
输出: ""说明:
所有输入只包含小写字母 a-z 。

Answer 1

function prefix(arr){
var r = ''
if (arr.sort)
{
r = arr[0].toLowerCase()
for(var i=1;i<arr.length;i++){
var x='';
for(var j=0;j<r.length&&j<arr[i].length;j++){
if (r[j]==arr[i].toLowerCase()[j])
{
x+=r[j]
}else{
break
}
}
r=x
if (!x)
{
break;
}
}
}
return r
}
alert(prefix(['xxoo','xxuroo','xxalloo','xxinoo']))

Answer 2

    //正则匹配简单但没性能
    function getPrefix(arr) {
        if (Array.isArray(arr)) {
            let len = arr.length
            if (len > 1) {
                let reg = arr.join(',').match(new RegExp('^(.+).*,' + Array(len - 1).fill('\\1.*').join(',')))
                return reg ? reg[1] : ''
            } else {
                return arr[0]
            }
        }
    }
    console.log(getPrefix(["flower","flow","flight"]))
    console.log(getPrefix(["dog","racecar","car"]))
    console.log(getPrefix(["我艹cdog","我艹cecar","我艹car"]))
    console.log(getPrefix(["racecar"]))

Answer 3

alert(prefix([]))    //出错

Answer 4

console.log(getPrefix([]))  //出错

Answer 5

    function getPrefix(arr) {
        if (Array.isArray(arr)) {
            let newArr = arr.slice(0) //克隆一份
            let len = arr.length
            if (len > 1) {
                newArr.sort((a, b) => a.length > b.length ? 1 : -1) //排序一下
                let per = newArr.shift()
                let match
                while(per && !match){
                    match = true
                    newArr.forEach(v=>{
                        if(!v.startsWith(per)){
                            match = false
                        }
                    })
                    if(!match){
                        per = per.slice(0,-1)
                    }
                }
                return per
            } else {
                return arr[0]
            }
        }
    }
    console.log(getPrefix(["flower","flow","flight"]))
    console.log(getPrefix(["dog","racecar","car"]))
    console.log(getPrefix(["我艹cdog","我艹cecar","我艹car"]))
    console.log(getPrefix(["racecar"]))或者使用split分割判断都可。

Answer 6

console.log(getPrefix([]))  //出错

Answer 7

    //正则匹配简单但没性能
    function getPrefix(arr) {
        if (Array.isArray(arr)) {
            let len = arr.length
            if (len > 1) {
                let reg = arr.join(',').match(new RegExp('^(.+).*,' + Array(len - 1).fill('\\1.*').join(',')))
                return reg ? reg[1] : ''
            } else {
                return len === 1 ? arr[0] : ''
            }
        }
    }

Answer 8

用正则表达式解很简单的function prefix(arr){
var r = arr.join(",").match(/^([^,]+)[^,]*(,\1[^,]*)*$/);
return r ? r[1] : "";
}
alert(prefix(["flower","flow","flight"]))

Answer 9

alert(prefix([]))    //出错 if (arr.sort)修改成
if (arr.sort && arr.length)之前没有判断数组元素为0的情况，自己调整下，不要什么都等别人弄好了