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export default function maxAreaOfIsland(grid: number[][]): number {    const m = grid.length;    if (m === 0) return 0;    const n = grid[0].length;    if (n === 0) return 0;    return Math.max(...getIslandsAreas(grid), 0);}function getIslandsAreas(grid: number[][]): number[] {    const m = grid.length;    if (m === 0) return [];    const n = grid[0].length;    if (n === 0) return [];
    const cache = new Set<number>();
    const islandareas: Array<number> = [];
    for (let r = 0; r < m; ++r) {        for (let c = 0; c < n; ++c) {            if (cache.has(unique_id(r, c, n))) {                continue;            }            if (grid[r][c] == 1) {                // ++num_islands;                let islandarea = 0;                dfs(                    grid,                    r,                    c,                    cache,                    (/* p: [number, number] */) => islandarea++,                    /*  island.push(p) */                );                islandareas.push(islandarea);            }        }    }    // console.log(islands)    return islandareas;}
function dfs(    grid: number[][],    r: number,    c: number,    cache: Set<number>,    output: (/* p: [number, number] */) => void,): void {    const m = grid.length;    if (m === 0) return;    const n = grid[0].length;    if (n === 0) return;
    if (r < 0 || c < 0 || r >= m || c >= n || grid[r][c] == 0) {        return;    }    const id = unique_id(r, c, n);    if (cache.has(id)) {        return;    }    cache.add(id);    output(); /* [r, c] */    dfs(grid, r - 1, c, cache, output);    dfs(grid, r + 1, c, cache, output);    dfs(grid, r, c - 1, cache, output);    dfs(grid, r, c + 1, cache, output);}function unique_id(r: number, c: number, n: number): number {    const a = c + r * n;    // console.log(c, r, n, a)    return a;}