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.

class Solution {

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