Write a function to find the longest common prefix string amongst an array of strings

package leetcode.chenyu.test;public class LongestCommonPrefix {public static void main(String[] args)  {String [] ss = {"12345", "3234", "234"};String [] ss1 = {"flower", "flow", "flight"};String [] ss2 = {"ca", "a"};String [] ss3 = {"a", "a"};String [] ss4 = {"aa","ab"};String [] ss5 = {"abca","aba","aaab"};String result =longestCommonPrefix(ss5);System.out.printf("result1111:" + result);}public static boolean isNull(String s) {if(s == null || s.length() == 0) {return true;}return false;} public  static String longestCommonPrefix(String[] strs) {if(strs == null || strs.length ==0) {return "";}int length = strs.length;if (length == 1) {return strs[0];}int minLength = Integer.MAX_VALUE;int index = 0;for (int i = 0; i < strs.length; ++i) {if (isNull(strs[i])) {return "";}if (minLength > strs[i].length()) {minLength = strs[i].length();index = i;}}String result = "";for (int i = 1; i <= minLength; ++i) {int count = 0;for (int j = i; j <= minLength; ++j) {String s =  strs[index].substring(count++, j);System.out.print("s:" + s + "\t");int flag = 0;for (int k = 0; k < length; k++) {if (k != index) {if (!strs[k].contains(s)) {break;} else {flag++;System.out.print("flag:" + flag + "\t");if (flag == length - 1) {if (result.length() < s.length()) {int num = 0;for (int h = 0; h < length; h++) {if (!strs[h].startsWith(s)) {break;} else {num++;}}if (num == length)result = s;}System.out.println("result:" + result + "\t");break;}}} }}}return result;}
}

特么一开始看错题目，虽然结果验证没有出问题，但是超时了，日了狗

下面的代码是求 字符串数组种最大的公共子串

package leetcode.chenyu.test;public class LongestCommonPrefix {public static void main(String[] args)  {String [] ss = {"12345", "3234", "234"};String [] ss1 = {"flower", "flow", "flight"};String [] ss2 = {"ca", "a"};String [] ss3 = {"a", "a"};String [] ss4 = {"aa","ab"};String [] ss5 = {"abca","aba","aaab"};String result =longestCommonPrefix(ss5);System.out.printf("result1111:" + result);}public static boolean isNull(String s) {if(s == null || s.length() == 0) {return true;}return false;} public  static String longestCommonPrefix(String[] strs) {if(strs == null || strs.length ==0) {return "";}int length = strs.length;if (length == 1) {return strs[0];}int minLength = Integer.MAX_VALUE;int index = 0;for (int i = 0; i < strs.length; ++i) {if (isNull(strs[i])) {return "";}if (minLength > strs[i].length()) {minLength = strs[i].length();index = i;}}String result = "";for (int i = 1; i <= minLength; ++i) {int count = 0;for (int j = i; j <= minLength; ++j) {String s =  strs[index].substring(count++, j);System.out.print("s:" + s + "\t");int flag = 0;for (int k = 0; k < length; k++) {if (k != index) {if (!strs[k].contains(s)) {break;} else {flag++;System.out.print("flag:" + flag + "\t");if (flag == length - 1) {if (result.length() < s.length()) {result = s;}System.out.println("result:" + result + "\t");break;}}} }}}return result;}
}

最后修改后可以通过LeetCode的代码

public class Solution {public static boolean isNull(String s) {if(s == null || s.length() == 0) {return true;}return false;} public  static String longestCommonPrefix(String[] strs) {if(strs == null || strs.length ==0) {return "";}int length = strs.length;if (length == 1) {return strs[0];}int minLength = Integer.MAX_VALUE;int index = 0;for (int i = 0; i < strs.length; ++i) {if (isNull(strs[i])) {return "";}if (minLength > strs[i].length()) {minLength = strs[i].length();index = i;}}String result = "";for (int i = 1; i <= minLength; ++i) {String s =  strs[index].substring(0, i);int flag = 0;for (int k = 0; k < length; k++) {if (k != index) {if (!strs[k].contains(s) || !strs[k].startsWith(s)) {break;} else {flag++;if (flag == length - 1) {if (result.length() < s.length()) {result = s;}break;}}} }}return result;}
}