695. Max Area of Island

Given a binary grid where 1 is land and 0 is water, return the area of the largest island (4-directionally connected land). Return 0 if there is no island.

Same scan, but measure each island with a queue: count cells as they are dequeued and enqueue unvisited land neighbors.

1function maxAreaOfIsland(grid: number[][]): number {
2  const m = grid.length, n = grid[0].length;
3  let best = 0;
4  for (let r = 0; r < m; r++)
5    for (let c = 0; c < n; c++) {
6      if (grid[r][c] !== 1) continue;
7      grid[r][c] = 0;
8      const queue = [[r, c]];
9      let area = 0;
10      while (queue.length) {
11        const [i, j] = queue.shift()!; area++;
12        for (const [x, y] of [[i + 1, j], [i - 1, j], [i, j + 1], [i, j - 1]])
13          if (x >= 0 && y >= 0 && x < m && y < n && grid[x][y] === 1) { grid[x][y] = 0; queue.push([x, y]); }
14      }
15      best = Math.max(best, area);
16    }
17  return best;
18}

area = 0best = 0

grid

1	1	0	0	0
1	1	0	0	0
0	0	0	1	1
0	0	1	1	1

queue

(0,0)

New island at (0, 0).

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