Beginner Exercism • javascript
Go Counting

Challenge Overview

Count the scored points on a Go board.
Source: Exercism javascript/go-counting
💡 View Solution
export class GoCounting {
  constructor(board) {
    this.board = board.split('\n').map(row => [...row]);
    this.rows = this.board.length;
    this.cols = this.board[0] ? this.board[0].length : 0;
  }

  getTerritory(x, y) {
    if (y < 0 || y >= this.rows || x < 0 || x >= this.cols) return { owner: 'NONE', territory: [] };
    if (this.board[y][x] !== ' ') return { owner: 'NONE', territory: [] };

    const territory = [];
    const visited = new Set();
    const queue = [[x, y]];
    const stoneColors = new Set();

    while (queue.length > 0) {
      const [cx, cy] = queue.shift();
      const key = `${cx},${cy}`;
      if (visited.has(key)) continue;
      visited.add(key);

      if (this.board[cy][cx] === ' ') {
        territory.push([cx, cy]);
        [[cx + 1, cy], [cx - 1, cy], [cx, cy + 1], [cx, cy - 1]].forEach(([nx, ny]) => {
          if (nx >= 0 && nx < this.cols && ny >= 0 && ny < this.rows) queue.push([nx, ny]);
        });
      } else {
        stoneColors.add(this.board[cy][cx]);
      }
    }

    let owner = 'NONE';
    if (stoneColors.size === 1) {
      const color = stoneColors.values().next().value;
      owner = color === 'B' ? 'BLACK' : 'WHITE';
    }

    return { owner, territory: territory.sort((a, b) => a[0] - b[0] || a[1] - b[1]) };
  }

  getTerritories() {
    const result = { TERRITORY_BLACK: [], TERRITORY_WHITE: [], TERRITORY_NONE: [] };
    const visited = new Set();

    for (let y = 0; y < this.rows; y++) {
      for (let x = 0; x < this.cols; x++) {
        if (this.board[y][x] === ' ' && !visited.has(`${x},${y}`)) {
          const { owner, territory } = this.getTerritory(x, y);
          territory.forEach(([tx, ty]) => visited.add(`${tx},${ty}`));
          result[`TERRITORY_${owner}`].push(...territory);
        }
      }
    }
    return result;
  }
}