[프로그래머스] 후보키 - JAVA

문제

https://school.programmers.co.kr/learn/courses/30/lessons/42890

프로그래머스

 

 

코드

import java.util.*;

class Solution {
    String table [][];
    List<List<Integer>> keyList = new ArrayList<>();
    public int solution(String[][] relation) {
        table = relation;
        if(relation[0].length == 1){
            if(unique(List.of(0)))
                return 1;
            else return 0;
        }
            
        for(int i=1;i<=relation[0].length;i++){
            back(new ArrayList<>(), i, 0);
        }
        
        return keyList.size();
    }
    
    public void back(ArrayList<Integer> list, int cnt, int idx){  
        if(cnt == 0){
            if (unique(list) && minimum(list)){
                keyList.add(list);
            }
            return;
        }
        for(int i=idx;i<table[0].length;i++){
            ArrayList<Integer> newList = new ArrayList<>(list);        
            newList.add(i);
            back(newList, cnt-1, idx+1);
        }
    }
    
    public boolean unique(List<Integer> key){
        List<String> list = new ArrayList<>();
        for(String [] row : table){
            String str = "";
            for(int idx : key){
                str += row[idx];
            }
            if(list.contains(str)) return false;
            else list.add(str);
        }
        return true;
    }
    
    public boolean minimum(List<Integer> newKeys){
        for(List<Integer> keys : keyList){
           if(newKeys.containsAll(keys)) return false;
        }
        return true;
    }
}