leetcode-14-java

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.

public class Leetcode14 {

    public static String longestCommonPrefix(String[] strs) {
        if (null == strs || strs.length == 0) {
            return "";
        }

        if (strs.length == 1) {
            return strs[0];
        }

        String maxSub = sub(strs[0], strs[1]);
        if ("".equals(maxSub)) {
            return "";
        }
        for (int i = 1; i < strs.length; i++) {
            maxSub  = sub(maxSub,  strs[i]);
            if ("".equals(maxSub)) {
                return "";
            }
        }
        return maxSub;
    }




    /**
     * 获取公共前缀
     * @param s1
     * @param s2
     * @return
     */
    private static String sub(String s1, String s2) {
        int len = Math.min(s1.length(), s2.length());
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < len; i++) {
            if (s1.charAt(i) == s2.charAt(i)) {
                sb.append(s1.charAt(i));
                continue;
            }
            break;
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        System.out.println(longestCommonPrefix(new String[] {"aca","cba"}));
    }
}