Longest Common Prefix Leetcode

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

这道题利用stringbuffer的delete方法

public class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs == null) {
            return null;
        }
        if (strs.length == 0) {
            return "";
        }
        StringBuilder s = new StringBuilder(strs[0]);
        for (int i = 1; i < strs.length; i++) {
            int j = 0;
            for (j = 0; j < s.length() && j < strs[i].length(); j++) {
                if (strs[i].charAt(j) != s.charAt(j)) {
                    s.delete(j, s.length());
                    break;
                }
            }
            s.delete(j, s.length());
        }
        return s.toString();
    }
}

topsolution是用substring的

public class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs == null) {
            return null;
        }
        if (strs.length == 0) {
            return "";
        }
        String s = strs[0];
        int i = 0;
        while (i < strs.length) {
            while (strs[i].indexOf(s) != 0) {
                s = s.substring(0, s.length() - 1);
            }
            i++;
        }
        return s;
    }
}

还可以用Arrays.sort的方法

public class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs == null) {
            return null;
        }
        if (strs.length == 0) {
            return "";
        }
        Arrays.sort(strs);
        for (int i = 0; i < strs[0].length(); i++) {
            if (strs[0].charAt(i) != strs[strs.length - 1].charAt(i)) {
                return strs[0].substring(0, i);
            }
        }
        return strs[0];
    }
}