leetcode/javascript/0695-max-area-of-island.js at main · neetcode-gh/leetcode · GitHub

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/**
 * https://leetcode.com/problems/max-area-of-island
 * Time O(ROWS * COLS) | Space O(ROWS * COLS)
 * @param {number[][]} grid
 * @return {number}
 */
var maxAreaOfIsland = function (grid, maxArea = 0) {
    const [rows, cols] = [grid.length, grid[0].length];
    const seen = new Array(rows).fill().map(() => new Array(cols));

    for (let row = 0; row < rows; row++) {
        /* Time O(ROWS) */
        for (let col = 0; col < cols; col++) {
            /* Time O(COLS) */
            const area = getArea(
                grid,
                row,
                rows,
                col,
                cols,
                seen,
            ); /* Space O(ROWS * COLS) */

            maxArea = Math.max(maxArea, area);
        }
    }

    return maxArea;
};

var getArea = (grid, row, rows, col, cols, seen) => {
    const isBaseCase = grid[row][col] === 0;
    if (isBaseCase) return 0;

    if (seen[row][col]) return 0;
    seen[row][col] = true; /* Space O(ROWS * COLS) */

    return dfs(grid, row, rows, col, cols, seen) + 1; /* Space O(ROWS * COLS) */
};

const dfs = (grid, row, rows, col, cols, seen, area = 0) => {
    for (const [_row, _col] of getNeighbors(row, rows, col, cols)) {
        area += getArea(grid, _row, rows, _col, cols, seen);
    }

    return area;
};

var getNeighbors = (row, rows, col, cols) =>
    [
        [0, 1],
        [0, -1],
        [1, 0],
        [-1, 0],
    ]
        .map(([_row, _col]) => [row + _row, col + _col])
        .filter(
            ([_row, _col]) =>
                0 <= _row && _row < rows && 0 <= _col && _col < cols,
        );

/**
 * https://leetcode.com/problems/number-of-islands/
 * Time O(ROWS * COLS) | Space O(ROWS * COLS)
 * @param {character[][]} grid
 * @return {number}
 */
var maxAreaOfIsland = (grid, maxArea = 0) => {
    const [rows, cols] = [grid.length, grid[0].length];
    const seen = new Array(rows).fill().map(() => new Array(cols));

    for (let row = 0; row < rows; row++) {
        /* Time O(ROWS) */
        for (let col = 0; col < cols; col++) {
            /* Time O(COLS) */
            const isBaseCase = grid[row][col] === 0;
            if (isBaseCase) continue;

            if (seen[row][col]) continue;
            seen[row][col] = true; /* Space O(ROWS * COLS) */

            const area = getArea(
                new Queue([[row, col]]),
                grid,
                seen,
            ); /* Space O(ROWS * COLS) */

            maxArea = Math.max(maxArea, area);
        }
    }

    return maxArea;
};

var getArea = (queue, grid, seen, area = 0) => {
    const [rows, cols] = [grid.length, grid[0].length];

    while (!queue.isEmpty()) {
        for (let i = queue.size() - 1; 0 <= i; i--) {
            /* Time O(WIDTH) */
            const [row, col] = queue.dequeue();

            for (const [_row, _col] of getNeighbors(row, rows, col, cols)) {
                const isBaseCase = grid[_row][_col] === 0;
                if (isBaseCase) continue;

                if (seen[_row][_col]) continue;
                seen[_row][_col] = true; /* Space O(ROWS * COLS) */

                queue.enqueue([_row, _col]); /* Space O(HEIGHT) */
            }

            area++;
        }
    }

    return area;
};

var getNeighbors = (row, rows, col, cols) =>
    [
        [0, 1],
        [0, -1],
        [1, 0],
        [-1, 0],
    ]
        .map(([_row, _col]) => [row + _row, col + _col])
        .filter(
            ([_row, _col]) =>
                0 <= _row && _row < rows && 0 <= _col && _col < cols,
        );