题目链接:https://leetcode-cn.com/problems/longest-common-prefix/

题目描述:

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:

示例 1:

输入: ["flower","flow","flight"]

输出: "fl"

示例 2:

输入: ["dog","racecar","car"]

输出: ""

解释: 输入不存在公共前缀。

说明:

所有输入只包含小写字母 a-z 。

思路:

思路1:

python特性,取每一个单词的同一位置的字母,看是否相同.

思路2:

取一个单词s,和后面单词比较,看s与每个单词相同的最长前缀是多少!遍历所有单词

思路3:

按字典排序数组,比较第一个,和最后一个单词,有多少前缀相同.

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代码:

python

思路一:

class Solution:

    def longestCommonPrefix(self, strs):

        """

        :type strs: List[str]

        :rtype: str

        """

        res = ""

        for tmp in zip(*strs):

            tmp_set = set(tmp)

            if len(tmp_set) == 1:

                res += tmp[0]

            else:

                break

        return res

思路二:

python

class Solution:

    def longestCommonPrefix(self, s: List[str]) -> str:

        if not s:

            return ""

        res = s[0]

        i = 1

        while i < len(s):

            while s[i].find(res) != 0:

                res = res[0:len(res)-1]

            i += 1

        return res

java

class Solution {

    public String longestCommonPrefix(String[] strs) {

        if (strs == null || strs.length == 0) return "";

        String res = strs[0];

        int i = 1;

        while (i < strs.length) {

            while (strs[i].indexOf(res) != 0) {

                res = res.substring(0, res.length() - 1);

            }

            i += 1;

        }

        return res;

    }

}

思路三:

python

class Solution:

    def longestCommonPrefix(self, s: List[str]) -> str:

        if not s:

            return ""

        s.sort()

        n = len(s)

        a = s[0]

        b = s[n-1]

        res = ""

        for i in range(len(a)):

            if i < len(b) and a[i] == b[i]:

                res += a[i]

            else:

                break

        return res

java

class Solution {

    public String longestCommonPrefix(String[] strs) {

        if (strs == null || strs.length == 0) return "";

        StringBuilder res = new StringBuilder();

        Arrays.sort(strs);

        // 字符串转数组

        char[] a = strs[0].toCharArray();

        char[] b = strs[strs.length - 1].toCharArray();

        for (int i = 0; i < a.length; i++) {

            if (i < b.length && a[i] == b[i]) {

                res.append(a[i]);

            }

            else{

                break;

            }

        }

        return res.toString();

    }

}