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‎src/main/java/org/example/_50week/Airport.java‎

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package org.example._50week;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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public class Airport {
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private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
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private static int[] gates;
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public static void main(String[] args) throws IOException {
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int gateCnt = Integer.parseInt(br.readLine());
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int airplaneCnt = Integer.parseInt(br.readLine());
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int answer = 0;
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gates = new int[gateCnt + 1];
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// 1. gate 초기화
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for (int i = 0; i < gates.length; i++) {
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gates[i] = i;
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}
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gates[0] = -1;
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for (int i = 0; i < airplaneCnt; i++) {
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int gi = Integer.parseInt(br.readLine());
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int parent = find(gi);
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if (parent == -1) {
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break;
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}
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gates[parent] = find(parent - 1);
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answer++;
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}
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System.out.println(answer);
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}
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private static int find(int gi) {
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if (gi == -1) {
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return -1;
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}
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if (gi == gates[gi]) {
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return gi;
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}
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return gates[gi] = find(gates[gi]);
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}
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}

‎src/main/java/org/example/_50week/FindNetwork.java‎

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package org.example._50week;
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import java.io.*;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.StringTokenizer;
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public class FindNetwork {
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private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
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private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
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private static Map<String, Integer> groupCntMap;
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private static Map<String, String> group;
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public static void main(String[] args) throws IOException {
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int testCnt = Integer.parseInt(br.readLine());
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for (int i = 0; i < testCnt; i++) {
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calculate();
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}
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bw.flush();
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}
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private static void calculate() throws IOException {
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groupCntMap = new HashMap<>();
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group = new HashMap<>();
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int relationCnt = Integer.parseInt(br.readLine());
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for (int i = 0; i < relationCnt; i++) {
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StringTokenizer st = new StringTokenizer(br.readLine());
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String friend1 = st.nextToken();
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String friend2 = st.nextToken();
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group.putIfAbsent(friend1, friend1);
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group.putIfAbsent(friend2, friend2);
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String parent = union(friend1, friend2);
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bw.write(groupCntMap.get(parent) + "\n");
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}
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}
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private static String union(String friend1, String friend2) {
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String parent1 = find(friend1, group);
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String parent2 = find(friend2, group);
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if(parent1.equals(parent2)){
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return parent1;
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}
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if (parent1.compareTo(parent2) <= 0 ) {
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group.put(parent1, parent2);
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groupCntMap.put(parent2, groupCntMap.getOrDefault(parent1, 1) + groupCntMap.getOrDefault(parent2, 1));
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return parent2;
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} else {
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group.put(parent2, parent1);
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groupCntMap.put(parent1, groupCntMap.getOrDefault(parent1, 1) + groupCntMap.getOrDefault(parent2, 1));
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return parent1;
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}
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}
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private static String find(String person, Map<String, String> group) {
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if (group.get(person).equals(person)) {
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return person;
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}
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String parent = find(group.get(person), group);
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group.put(person, parent);
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return parent;
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}
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}

‎src/main/java/org/example/_50week/PreparingMeeting.java‎

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package org.example._50week;
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public class PreparingMeeting {
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public static void main(String[] args) {
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}
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}

‎src/main/java/org/example/_50week/TheSwanLake.java‎

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package org.example._50week;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.util.*;
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public class TheSwanLake {
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private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
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private static final int WATER = 0;
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private static final int ICE = 1;
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private static final int SWAN = 2;
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private static final int[] dr = {-1, 0, 1, 0};
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private static final int[] dc = {0, 1, 0, -1};
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private static int rowSize;
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private static int colSize;
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private static int[][] map;
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private static int[][] group;
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private static Queue<int[]> melts;
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private static Queue<int[]> nextMelts;
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private static final List<Integer> swanGroups = new ArrayList<>();
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private static final Map<Integer, Integer> parent = new HashMap<>();
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public static void main(String[] args) throws IOException {
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input();
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int groupNo = 3;
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for (int row = 0; row < rowSize; row++) {
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for (int col = 0; col < colSize; col++) {
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if (map[row][col] != ICE && group[row][col] == 0) { // WATER, SWAN
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markGroup(row, col, groupNo);
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groupNo++;
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}
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}
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}
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// 처음에 바로 만나있으면
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// sout 0
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Integer firstSwanGroup = swanGroups.get(0);
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Integer secondSwanGroup = swanGroups.get(1);
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if (firstSwanGroup.equals(secondSwanGroup)) {
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System.out.println(0);
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}
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// 1일차.
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for (int row = 0; row < rowSize; row++) {
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for (int col = 0; col < colSize; col++) {
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if (map[row][col] == ICE) {
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boolean isConnected = melt(row, col);
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if (isConnected) {
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System.out.println(1);
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return;
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}
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}
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}
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}
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for (int[] melt : melts) {
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map[melt[0]][melt[1]] = WATER;
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}
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for (int day = 2; ; day++) {
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melts = nextMelts;
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nextMelts = new LinkedList<>();
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for (int[] melt : melts) {
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int row = melt[0];
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int col = melt[1];
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if (map[row][col] == ICE) {
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boolean isConnected = melt(row, col);
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if (isConnected) {
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System.out.println(day);
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return;
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}
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}
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}
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for (int[] melt : melts) {
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map[melt[0]][melt[1]] = WATER;
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}
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}
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}
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private static boolean melt(int row, int col) {
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for (int i = 0; i < 4; i++) {
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int nextRow = row + dr[i];
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int nextCol = col + dc[i];
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if (nextRow < 0 || nextRow >= rowSize || nextCol < 0 || nextCol >= colSize) {
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continue;
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}
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if (map[nextRow][nextCol] == ICE) {
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continue;
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}
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melts.add(new int[]{row, col});
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group[row][col] = group[nextRow][nextCol];
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}
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if (group[row][col] == 0) {
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return false;
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}
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for (int i = 0; i < 4; i++) {
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int nextRow = row + dr[i];
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int nextCol = col + dc[i];
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if (nextRow < 0 || nextRow >= rowSize || nextCol < 0 || nextCol >= colSize) {
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continue;
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}
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int adjacent = group[nextRow][nextCol];
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if (adjacent == 0) {
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nextMelts.add(new int[]{nextRow, nextCol});
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continue;
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}
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if (group[row][col] == adjacent) {
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continue;
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}
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union(group[row][col], adjacent);
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Integer firstSwanGroup = swanGroups.get(0);
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Integer secondSwanGroup = swanGroups.get(1);
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if (isSame(firstSwanGroup, secondSwanGroup)) {
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return true;
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}
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}
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return false;
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}
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private static void union(int first, int second) {
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if (first == 0) {
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parent.put(first, second);
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return;
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} else if (second == 0) {
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parent.put(second, first);
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return;
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}
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int firstParent = find(first);
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int secondParent = find(second);
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if (firstParent <= secondParent) {
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parent.put(secondParent, firstParent);
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} else {
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parent.put(firstParent, secondParent);
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}
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}
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private static boolean isSame(int first, int second) {
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int firstParent = find(first);
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int secondParent = find(second);
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return firstParent == secondParent;
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}
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private static int find(int unit) {
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if (parent.get(unit) == unit) {
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return unit;
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}
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int p = parent.get(parent.get(unit));
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parent.put(unit, p);
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return p;
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}
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private static void markGroup(int row, int col, int groupNo) {
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// 진영 선택
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// 백조 진영 확인
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// union find 배열도 만들어줘야함.
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parent.put(groupNo, groupNo);
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Queue<int[]> queue = new LinkedList<>();
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queue.add(new int[]{row, col});
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group[row][col] = groupNo;
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while (!queue.isEmpty()) {
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int[] pos = queue.poll();
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int curRow = pos[0];
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int curCol = pos[1];
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group[curRow][curCol] = groupNo;
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if (map[curRow][curCol] == SWAN) {
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swanGroups.add(groupNo);
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}
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for (int i = 0; i < 4; i++) {
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int nextRow = curRow + dr[i];
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int nextCol = curCol + dc[i];
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if (nextRow < 0 || nextRow >= rowSize || nextCol < 0 || nextCol >= colSize) {
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continue;
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}
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if (map[nextRow][nextCol] == ICE) {
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continue;
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}
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if (group[nextRow][nextCol] != 0) {
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continue;
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}
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group[nextRow][nextCol] = groupNo;
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queue.add(new int[]{nextRow, nextCol});
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}
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}
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}
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private static void input() throws IOException {
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StringTokenizer st = new StringTokenizer(br.readLine());
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rowSize = Integer.parseInt(st.nextToken());
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colSize = Integer.parseInt(st.nextToken());
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map = new int[rowSize][colSize];
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group = new int[rowSize][colSize];
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// melts = new boolean[rowSize][colSize];
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melts = new LinkedList<>();
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nextMelts = new LinkedList<>();
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for (int row = 0; row < rowSize; row++) {
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String input = br.readLine();
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for (int col = 0; col < colSize; col++) {
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char cell = input.charAt(col);
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if (cell == 'X') {
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map[row][col] = ICE;
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} else if (cell == '.') {
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map[row][col] = WATER;
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} else {
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map[row][col] = SWAN;
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}
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}
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}
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}
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}

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