(LeetCode)Longest Common Prefix

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

https://leetcode.com/problems/longest-common-prefix/description/

給定輸入是一個字符串數組，輸出元素最長起始公共串。如{"aab","ac","aac"}，則輸出"a"

思路：首先取第一個元素，不斷對其取subString（縮小串長度）與後面的元素起始比較，用了indexOf這個方法，返回0則說明它是這個String的起始子串

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

    }

當然也可以用startsWith

 public String longestCommonPrefix(String[] strs) {
          if(strs ==null || strs.length == 0){
            return "";
        }
        String maxLengthStr = strs[0];
        for(int i=1;i<strs.length;i++){
            while (!strs[i].startsWith(maxLengthStr)){
                maxLengthStr = maxLengthStr.substring(0,maxLengthStr.length()-1);
            }
        }
        return maxLengthStr;

    }