[LeetCode] 14. Longest Common Prefix

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

public class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs == null || strs.length == 0) {
            return "";
        } else if (strs.length < 2) {
            return strs[0];
        }

        String r = strs[0];
        int index = r.length();
        for (int i = 1; i < strs.length; i++) {
            int j = 0;
            for (; j < strs[i].length() && j < index; j++) {
                if (strs[i].charAt(j) != r.charAt(j)) {
                    break;
                }
            }
            if (j == 0) {
                return "";
            }
            index = j;
        }

        return r.substring(0, index);
    }
}