Study/260309

problems/SWEA/p1868/Solution.java

@@ -0,0 +1,181 @@
+/*
+ * (1868) 파핑파핑 지뢰찾기
+ * https://swexpertacademy.com/main/code/problem/problemDetail.do?contestProbId=AV5LwsHaD1MDFAXc&categoryId=AV5LwsHaD1MDFAXc&categoryType=CODE&problemTitle=1868&orderBy=FIRST_REG_DATETIME&selectCodeLang=ALL&select-1=&pageSize=10&pageIndex=1
+ */
+
+import java.io.*;
+import java.util.*;
+
+/**
+ * SW Expert Academy - 파핑파핑 지뢰찾기
+ * @author YeJun, Jung
+ * 
+ * [분석]
+ *   - 지뢰찾기 게임과 규칙은 동일하다.
+ *   - 최소한의 클릭으로 지뢰가 없는 칸들을 모두 여는 방법을 찾아야 한다.
+ * 
+ * [전략]
+ *   - 각 칸은 ID를 가지고 있다.
+ *   - 각 ID에 대해서 부모 노드의 ID를 보관하는 배열 parentArr가 있다.
+ *     - 처음에 parentArr는 자기자신을 가르키도록 초기화 한다.
+ *   - 각 칸(ID)에 대해서 DFS으로 칸을 열어본다.
+ *     - 열어본 칸에 대해서는 ID로 기록을 한다.
+ *     - 칸을 열때 다른 ID가 기록되어 있다면 해당 칸의 ID와 현재 ID를 Union 한다.
+ *   - parentArr에 있는 ID 종류의 개수가 정답이 된다.
+ */
+public class Solution {
+  static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
+  static StringBuilder output = new StringBuilder();
+  static StringTokenizer input;
+
+  // ----------------------------------------------------------
+
+  public static void main(String[] args) throws IOException {
+    final int testCount = nextInt();
+
+    for (int testCase = 1; testCase <= testCount; testCase++) {
+      new Solution(testCase).run();
+    }
+
+    System.out.print(output.toString());
+  }
+
+  // ----------------------------------------------------------
+
+  static final int[] DIR_X = { -1,  1,  0,  0,  1,  1, -1, -1 };
+  static final int[] DIR_Y = {  0,  0, -1,  1,  1, -1,  1, -1 };
+  static final int DIR_LEN = 8;
+
+  int testCase;
+  int answer;
+  int boardSize;
+  int[][] board;
+
+  int[] parentArr;
+
+  public Solution(int testCase) { this.testCase = testCase; }
+  public void run() throws IOException { input(); solve(); print(); }
+
+  private void input() throws IOException {
+    char[] buf;
+
+    boardSize = nextInt();
+    board = new int[boardSize][boardSize];
+
+    for (int y = 0; y < boardSize; y++) {
+      buf = next().toCharArray();
+
+      for (int x = 0; x < boardSize; x++) {
+        if (buf[x] == '.') continue;
+
+        board[y][x] = -1;
+      }
+    }
+  }
+
+  private void solve() {
+    answer = 0;
+
+    makeParentArr();
+
+    for (int y = 0; y < boardSize; y++) {
+      for (int x = 0; x < boardSize; x++) {
+        int id = (y * boardSize) + x + 1;
+
+        if (board[y][x] != 0) {
+          parentArr[id] = 0;
+          continue;
+        }
+
+        board[y][x] = id;
+        openTile(x, y, id);
+      }
+    }
+
+    updateAnswer();
+  }
+
+  private void makeParentArr() {
+    final int N = boardSize * boardSize + 1;
+    parentArr = new int[N];
+
+    for (int idx = 0; idx < N; idx++) {
+      parentArr[idx] = idx;
+    }
+  }
+
+  private int findParent(int idx) {
+    if (parentArr[idx] == idx) return idx;
+    return findParent(parentArr[idx]);
+  }
+
+  private void unionParent(int a, int b) {
+    int pa = findParent(a);
+    int pb = findParent(b);
+    if (pa != pb) parentArr[pb] = pa;
+  }
+
+  private void openTile(int x, int y, int id) {
+    int cnt = 0;
+
+    for (int dir = 0; dir < DIR_LEN; dir++) {
+      int nx = x + DIR_X[dir];
+      int ny = y + DIR_Y[dir];
+
+      if (!isInsideBoard(nx, ny)) continue;
+      if (board[ny][nx] == -1) cnt++;
+    }
+
+    if (cnt != 0) return;
+
+    for (int dir = 0; dir < DIR_LEN; dir++) {
+      int nx = x + DIR_X[dir];
+      int ny = y + DIR_Y[dir];
+
+      if (!isInsideBoard(nx, ny) || board[ny][nx] == -1) continue;
+
+      if (board[ny][nx] != 0) {
+        unionParent(id, board[ny][nx]);
+        continue;
+      }
+
+      board[ny][nx] = id;
+      openTile(nx, ny, id);
+    }
+  }
+
+  private boolean isInsideBoard(int x, int y) {
+    return x >= 0 && x < boardSize && y >= 0 && y < boardSize;
+  }
+
+  private void updateAnswer() {
+    Set<Integer> set = new HashSet<>();
+    for (int idx = 1; idx < parentArr.length; idx++) {
+      if (parentArr[idx] == 0) continue;
+      set.add(parentArr[idx]);
+    }
+
+    answer = set.size();
+  }
+
+  private void print() {
+    output
+      .append('#')
+      .append(testCase)
+      .append(' ')
+      .append(answer)
+      .append('\n');
+  }
+
+  // ----------------------------------------------------------
+
+  static String next() throws IOException {
+    if (input == null || !input.hasMoreTokens())
+      input = new StringTokenizer(reader.readLine().trim());
+    return input.nextToken();
+  }
+
+  static int nextInt() throws IOException {
+    return Integer.parseInt(next());
+  }
+}

problems/SWEA/p3289/Solution.java

@@ -0,0 +1,112 @@
+/*
+ * (3289) 서로소 집합
+ * https://swexpertacademy.com/main/code/problem/problemDetail.do?contestProbId=AWBJKA6qr2oDFAWr&categoryId=AWBJKA6qr2oDFAWr&categoryType=CODE&problemTitle=3289&orderBy=FIRST_REG_DATETIME&selectCodeLang=ALL&select-1=&pageSize=10&pageIndex=1
+ */
+
+import java.io.*;
+import java.util.*;
+
+/**
+ * SW Expert Academy - 서로소 집합
+ * @author YeJun, Jung
+ * 
+ * [분석]
+ *   - 런타임에 합집합 연산과 같은 집합에 속해있는지 확인하는 연산을 빠르게 수행해야 하는 문제이다.
+ * 
+ * [전략]
+ *   - Union-Find 알고리즘 적용
+ *     - Path compression 최적화 사용
+ */
+public class Solution {
+  static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
+  static StringBuilder output = new StringBuilder();
+  static StringTokenizer input;
+
+  // ----------------------------------------------------------
+
+  public static void main(String[] args) throws IOException {
+    final int testCount = nextInt();
+
+    for (int testCase = 1; testCase <= testCount; testCase++) {
+      new Solution(testCase).run();
+    }
+
+    System.out.print(output.toString());
+  }
+
+  // ----------------------------------------------------------
+
+  int testCase;
+  int answer;
+  int nodeLen;
+  int cmdLen;
+  int[] parentArr;
+
+  public Solution(int testCase) { this.testCase = testCase; }
+  public void run() throws IOException { input(); solve(); print(); }
+
+  private void input() throws IOException {
+    nodeLen = nextInt();
+    cmdLen = nextInt();
+  }
+
+  private void solve() throws IOException {
+    output
+      .append('#')
+      .append(testCase)
+      .append(' ');
+
+    parentArr = new int[nodeLen + 1];
+    for (int idx = 1; idx <= nodeLen; idx++) {
+      parentArr[idx] = idx;
+    }
+
+    int cmd, arg0, arg1;
+
+    for (int cnt = 0; cnt < cmdLen; cnt++) {
+      cmd = nextInt();
+      arg0 = nextInt();
+      arg1 = nextInt();
+
+      if (cmd == 0) {
+        // union
+        unionParent(arg0, arg1);
+      } else {
+        // find
+        output.append(checkParent(arg0, arg1) ? '1' : '0');
+      }
+    }
+  }
+
+  private boolean checkParent(int a, int b) {
+    return findParent(a) == findParent(b);
+  }
+
+  private void unionParent(int a, int b) {
+    int pa = findParent(a);
+    int pb = findParent(b);
+
+    if (pa != pb) parentArr[pb] = pa;
+  }
+
+  private int findParent(int node) {
+    if (parentArr[node] == node) return node;
+    return parentArr[node] = findParent(parentArr[node]);
+  }
+
+  private void print() {
+    output.append('\n');
+  }
+
+  // ----------------------------------------------------------
+
+  static String next() throws IOException {
+    if (input == null || !input.hasMoreTokens())
+      input = new StringTokenizer(reader.readLine().trim());
+    return input.nextToken();
+  }
+
+  static int nextInt() throws IOException {
+    return Integer.parseInt(next());
+  }
+}