14. Longest Common Prefix

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

If there is no common prefix, return an empty string "".

Example 1:
Input: ["flower","flow","flight"]
Output: "fl"

Example 2:
Input: ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.

Note:
All given inputs are in lowercase letters a-z.

难度：easy

题目：
写方法从一字符串数组中找出最长公共前缀,如果没则返回空字符串。
所有给出的输入字符串都由小写字母组成。

思路：
先找出最短字符串，然后分别求前缀。

Runtime: 5 ms, faster than 79.60% of Java online submissions for Longest Common Prefix.

public class Solution {
    public String longestCommonPrefix(String[] strs) {
        if (strs.length < 1) {
            return "";
        }
        
        int minStrLen = strs[0].length(), minIdx = 0;
        for (int i = 0; i < strs.length; i++) {
            if (minStrLen > strs[i].length()) {
                minStrLen = strs[i].length();
                minIdx = i;
            }
        }
        String prefix = strs[minIdx];
        for (int i = 0; i < strs.length; i++) {
            for (int j = 0; j < prefix.length() && j < strs[i].length(); j++) {
                if (prefix.charAt(j) != strs[i].charAt(j)) {
                    prefix = prefix.substring(0, j);
                    break;
                }
            }
        }
        
        return prefix;
    }
}