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

LongestCommonPrefix.cs

public class TrieNode{
    public bool isEndOfWord;
    public TrieNode[] children;
    public TrieNode(){
        isEndOfWord = false;
        children = new TrieNode[26];
        for(int i=0;i<26;i++){
            children[i] = null;
        }
    }    
}

public class Solution {
    
    public TrieNode root;
    
    public void Insert(string str){
        
        TrieNode temp = root;
        int len = str.Length;
        for(int i=0;i<len;i++)
        {   
            int index = str[i]-'a';
            if(temp.children[index] == null){
                temp.children[index] = new TrieNode();
            }
            
            temp = temp.children[index];
        }
    
        temp.isEndOfWord=true;
        
    }

    public string GetPrefix(){
        
        if(root == null){
            return "";
        }
        
        TrieNode temp = root;

        string prefix = "";
        bool loop = true;
        while(loop && !temp.isEndOfWord){
            TrieNode found = null;
            int index = 0;
            for(int i=0;i<26;i++){
                if(temp.children[i]!=null){
                    
                    if(found == null){
                        found = temp.children[i];   
                        index = i;
                    }
                    else{
                        loop = false;
                    }
                }    
            }
            
            if(loop){
                prefix = prefix + (Convert.ToChar(index+'a')).ToString();    
            }
            temp = found;
        }
        
        return prefix;
        
    }

    public string LongestCommonPrefix(string[] strs) {
        root = new TrieNode();
        
        int len = strs.Length;
        
        if(len==0){
            return "";
        }
        for(int i=0;i<len;i++){
            Insert(strs[i]);
        }
        
        string prefix = GetPrefix();
        
        return prefix;
    }
}