LeetCode: Longest Common Prefix 解题报告

Longest Common Prefix Total Accepted: 24665 Total Submissions: 92370

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 Solution 

 

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。

public class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs == null) {
            return null;
        }
        
        if (strs.length == 0 || strs[0].length() == 0) {
            return "";
        }
        
        int len = strs[0].length();
        int i = 0;
        for (; i < len; i++) {
            char c = strs[0].charAt(i);
            
            int j = 1;
            for (; j < strs.length; j++) {
                if (strs[j].length() <= i || c != strs[j].charAt(i)) {
                    break;
                }
            }
            
            // there is err.
            if (j < strs.length) {
                break;
            }
        }
        
        // The char i is invalid. 因为读到i时退出，所以不应包含i本身。
        return strs[0].substring(0, i);
    }
}

SOULTION2:

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

重新改写：

public class Solution {
    //http://blog.csdn.net/fightforyourdream/article/details/14642079
    public String longestCommonPrefix(String[] strs) {
        if (strs == null) {
            return null;
        }
        
        if (strs.length == 0) {
            return "";
        }
        
        String s = strs[0];
        int len = s.length();
        
        for (int i = 0; i < len; i++) {
            char c = s.charAt(i);
            
            for (int j = 1; j < strs.length; j++) {
                if (strs[j].length() <= i || c != strs[j].charAt(i)) {
                    // The char i is invalid. 因为读到i时退出，所以不应包含i本身。
                    return s.substring(0, i);
                }
            }
        }
        
        // Didn't break, the whole String is valid.
        return s;
    }
}

请Floow主页君的GitHUB: 

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