[해시] 프로그래머스 전화번호 Java

import java.util.*;

public class Solution {
	public boolean solution(String[] phone_book) {
		Scanner sc = new Scanner(System.in);
		boolean answer = true;
		
		HashMap<String, Boolean> map = new HashMap<>();
		
		for(String str: phone_book) map.put(str, true);
		
		for(String str: phone_book) {
			for(int i=0; i<str.length(); i++) {
				if(map.containsKey(str.substring(0,i))) {
					// false 반환
					answer = false;
					return answer;
				}
			}
		}
		return answer; // true 반환
	}
}