[해시] 전화번호 목록 (JAVA)

import java.util.*;
class Solution {
    public boolean solution(String[] phone_book) {
        for(int i=0; i<phone_book.length-1; i++) {
            for(int j=i+1; j<phone_book.length; j++) {
                if(phone_book[i].startsWith(phone_book[j])) {return false;}
                if(phone_book[j].startsWith(phone_book[i])) {return false;}
            }
        }
        return true;
    }
}