LeetCode: Longest Common Prefix 解题报告

Longest Common Prefix Total Accepted: 24665 Total Submissions: 92370

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

 

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SOULTION1:

解法就是扫一次。不过各种边界条件很容易出错。

 1 public class Solution {

 2     public String longestCommonPrefix(String[] strs) {

 3         if (strs == null) {

 4             return null;

 5         }

 6         

 7         if (strs.length == 0 || strs[0].length() == 0) {

 8             return "";

 9         }

10         

11         int len = strs[0].length();

12         int i = 0;

13         for (; i < len; i++) {

14             char c = strs[0].charAt(i);

15             

16             int j = 1;

17             for (; j < strs.length; j++) {

18                 if (strs[j].length() <= i || c != strs[j].charAt(i)) {

19                     break;

20                 }

21             }

22             

23             // there is err.

24             if (j < strs.length) {

25                 break;

26             }

27         }

28         

29         // The char i is invalid. 因为读到i时退出，所以不应包含i本身。

30         return strs[0].substring(0, i);

31     }

32 }

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SOULTION2:

感谢大神的灵感http://blog.csdn.net/fightforyourdream/article/details/14642079

重新改写：

 1 public class Solution {

 2     //http://blog.csdn.net/fightforyourdream/article/details/14642079

 3     public String longestCommonPrefix(String[] strs) {

 4         if (strs == null) {

 5             return null;

 6         }

 7         

 8         if (strs.length == 0) {

 9             return "";

10         }

11         

12         String s = strs[0];

13         int len = s.length();

14         

15         for (int i = 0; i < len; i++) {

16             char c = s.charAt(i);

17             

18             for (int j = 1; j < strs.length; j++) {

19                 if (strs[j].length() <= i || c != strs[j].charAt(i)) {

20                     // The char i is invalid. 因为读到i时退出，所以不应包含i本身。

21                     return s.substring(0, i);

22                 }

23             }

24         }

25         

26         // Didn't break, the whole String is valid.

27         return s;

28     }

29 }

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请Floow主页君的GitHUB: 

https://github.com/yuzhangcmu/LeetCode_algorithm/blob/master/string/LongestCommonPrefix.java