[프로그래머스] 퍼즐 조각 채우기(위클리 챌린지 3주차)

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import java.util.*;

public class Solution {
  class Pos {
    int r, c;
    Pos(int r, int c) {
      this.r = r;
      this.c = c;
    }
  }

  class Block {
    int index;
    List<Pos> positions;

    Block(int index, List<Pos> positions) {
      this.index = index;
      this.positions = positions;
    }
  }

  private List<Block> blocks = new ArrayList<>();
  private int maxIndexOfBlock = 0;
  private boolean[] used;
  private int answer = 0;

  public int solution(int[][] game_board, int[][] table) {
    indexingBlocks(table);
    for (int i = 0; i < 4; i++) {
      table = rotate(table);
      addBlocksInTable(table);
    }

    doGame(game_board);

    return answer;
  }

  private void indexingBlocks(int[][] arr) {
    int index = 2;
    for (int i = 0; i < arr.length; i++) {
      for (int j = 0; j < arr[0].length; j++) {
        if (arr[i][j] == 1) {
          fillIndex(arr, i, j, index);
          index++;
        }
      }
    }
    maxIndexOfBlock = index;
    used = new boolean[maxIndexOfBlock];
  }

  private final int[] dr = {-1, 1, 0, 0};
  private final int[] dc = {0, 0, -1, 1};

  private void fillIndex(int[][] arr, int row, int col, int index) {
    // BFS
    final int R = arr.length;
    final int C = arr[0].length;
    boolean[][] visited = new boolean[R][C];
    Queue<Integer> queue = new LinkedList<>();

    arr[row][col] = index;
    visited[row][col] = true;
    queue.add(row);
    queue.add(col);

    while (!queue.isEmpty()) {
      int r = queue.poll();
      int c = queue.poll();
      for (int d = 0; d < 4; d++) {
        int nr = r + dr[d];
        int nc = c + dc[d];

        if (nr < 0 || nr >= R || nc < 0 || nc >= C ||
            visited[nr][nc] ||
            arr[nr][nc] == 0) {
          continue;
        }

        arr[nr][nc] = index;
        visited[nr][nc] = true;
        queue.add(nr);
        queue.add(nc);
      }
    }
  }

  private int[][] rotate(int[][] arr) {
    final int R = arr.length;
    final int C = arr[0].length;

    int[][] result = new int[R][C];
    for (int i = 0; i < R; i++) {
      for (int j = 0; j < C; j++) {
        result[i][j] = arr[C - j - 1][i];
      }
    }

    return result;
  }

  private void addBlocksInTable(int[][] table) {
    final int R = table.length;
    final int C = table[0].length;

    boolean[] visited = new boolean[maxIndexOfBlock];
    for (int i = 0; i < R; i++) {
      for (int j = 0; j < C; j++) {
        if (table[i][j] > 1 && !visited[table[i][j]]) {
          int idx = table[i][j];
          visited[idx] = true;
          List<Pos> positions = getPositions(table, idx);
          blocks.add(new Block(idx, positions));
        }
      }
    }
  }

  private List<Pos> getPositions(int[][] arr, int index) {
    List<Pos> result = new ArrayList<>();
    final int R = arr.length;
    final int C = arr[0].length;

    Pos start = null;
    for (int i = 0; i < R; i++) {
      for (int j = 0; j < C; j++) {
        if (arr[i][j] == index) {
          if (start == null) {
            start = new Pos(i, j);
            result.add(new Pos(0, 0));
          } else {
            result.add(new Pos(i - start.r, j - start.c));
          }
        }
      }
    }

    return result;
  }

  private void doGame(int[][] gameBoard) {
    final int R = gameBoard.length;
    final int C = gameBoard[0].length;

    for (int i = 0; i < R; i++) {
      for (int j = 0; j < C; j++) {
        tryBlockAtPoint(gameBoard, i, j);
      }
    }
  }

  private void tryBlockAtPoint(int[][] gameBoard, int row, int col) {
    for (Block block : blocks) {
      if (!used[block.index] && isFitBlock(gameBoard, row, col, block)) {
        used[block.index] = true;
        int result = insertBlock(gameBoard, row, col, block);
        answer += result;
      }
    }
  }

  private boolean isFitBlock(int[][] arr, int row, int col, Block block) {
    boolean result = false;

    if (checkAllEmpty(arr, row, col, block)) {
      insertBlock(arr, row, col, block);
      result = checkNoEmptyAround(arr, row, col, block);
      deleteBlock(arr, row, col, block);
    }

    return result;
  }

  private int insertBlock(int[][] arr, int row, int col, Block block) {
    for (Pos pos : block.positions) {
      int nr = row + pos.r;
      int nc = col + pos.c;
      arr[nr][nc] = block.index;
    }

    return block.positions.size();
  }

  private boolean checkNoEmptyAround(int[][] arr, int row, int col, Block block) {
    final int R = arr.length;
    final int C = arr[0].length;

    for (Pos pos : block.positions) {
      for (int d = 0; d < 4; d++) {
        int nr = row + pos.r + dr[d];
        int nc = col + pos.c + dc[d];
        if (nr < 0 || nr >= R || nc < 0 || nc >= C) {
          continue;
        }
        if (arr[nr][nc] == 0) {
          return false;
        }
      }
    }

    return true;
  }

  private void deleteBlock(int[][] arr, int row, int col, Block block) {
    for (Pos pos : block.positions) {
      int nr = row + pos.r;
      int nc = col + pos.c;
      arr[nr][nc] = 0;
    }
  }

  private boolean checkAllEmpty(int[][] arr, int row, int col, Block block) {
    final int R = arr.length;
    final int C = arr[0].length;

    for (Pos pos : block.positions) {
      int nr = row + pos.r;
      int nc = col + pos.c;
      if (nr < 0 || nr >= R || nc < 0 || nc >= C) {
        return false;
      }
      if (arr[nr][nc] != 0) {
        return false;
      }
    }

    return true;
  }
}