[프로그래머스] 표 병합

약간 삼성 B형 느낌이 났던 문제.

구현 문제라서 시간이 좀 걸렸고, 한 글자를 잘못 써서 헤멨던 문제다.

구현 문제를 풀 때는 꼼꼼하게, 주석을 작성하면서 푸는 습관을 들여야겠다.

import java.util.*;

class Solution {
    
    static String[][] table;
    static int[] parent;
    
       public static String[] solution(String[] commands) {
            List<String> answers = new ArrayList<>();

            table = new String[50][50];
            parent = new int[2500];

            for(int i = 0; i < 2500; i++) {
                parent[i] = i;
            }

            for(int i = 0; i < commands.length; i++) {
                String[] command = commands[i].split(" ");

                switch(command[0]) {
                    case "UPDATE":
                        if(command.length == 4) {
                            int r = Integer.parseInt(command[1]) - 1;
                            int c = Integer.parseInt(command[2]) - 1;
                            String v = command[3];
                            update(r, c, v);
                        } else {
                            String v1 = command[1];
                            String v2 = command[2];
                            updateAll(v1, v2);
                        }
                        break;
                    case "MERGE":
                        int r1 = Integer.parseInt(command[1]) - 1;
                        int c1 = Integer.parseInt(command[2]) - 1;
                        int r2 = Integer.parseInt(command[3]) - 1;
                        int c2 = Integer.parseInt(command[4]) - 1;
                        merge(r1, c1, r2, c2);
                        break;
                    case "UNMERGE":
                        int r3 = Integer.parseInt(command[1]) - 1;
                        int c3 = Integer.parseInt(command[2]) - 1;
                        unmerge(r3, c3);
                        break;
                    case "PRINT":
                        int r4 = Integer.parseInt(command[1]) - 1;
                        int c4 = Integer.parseInt(command[2]) - 1;
                        if(table[r4][c4] == null) {
                            answers.add("EMPTY");
                        } else {
                            answers.add(table[r4][c4]);
                        }
                        break;
                }
                
            }
            String[] answer = new String[answers.size()];
            for(int i = 0; i < answer.length; i++) {
                answer[i] = answers.get(i);
            }
            return answer;
        }

        public static void update(int r, int c, String value) {
            int stdCell = find(r * 50 + c);
            for(int i = 0; i < 2500; i++) {
                if(parent[i] == stdCell) {
                    int r1 = i / 50;
                    int c1 = i % 50;
                    table[r1][c1] = value;
                }
            }
        }

        public static void updateAll(String v1, String v2) {
            for(int r = 0; r < 50; r++) {
                for(int c = 0; c < 50; c++) {
                    if(v1.equals(table[r][c])) {
                        table[r][c] = v2;
                    }
                }
            }
        }

        public static void merge(int r1, int c1, int r2, int c2) {
            int rc1 = r1 * 50 + c1;
            int rc2 = r2 * 50 + c2;

            int prc1 = find(rc1);
            int prc2 = find(rc2);

            if(prc1 == prc2) return;

            parent[prc2] = prc1;

            String value = table[r1][c1] != null ? table[r1][c1] : table[r2][c2];
            for(int i = 0; i < 2500; i++) {
                if(find(i) == prc1) {
                    int r = i / 50;
                    int c = i % 50;
                    table[r][c] = value;
                }
            }
        }

        public static int find(int a) {
            if(parent[a] == a) return a;
            return parent[a] = find(parent[a]);
        }

        public static void unmerge(int r, int c) {
            String v = table[r][c];
            int stdCell = find(r * 50 + c);

            for(int i = 0; i < 2500; i++) {
                if(parent[i] == stdCell) {
                    int r1 = i / 50;
                    int c1 = i % 50;
                    parent[i] = i;
                    table[r1][c1] = null;
                }
            }
            table[r][c] = v;
        }
    
}