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function closedIsland(grid: number[][]): number {    const m = grid.length;    const n = grid[0].length;    let res = 0;    grid.forEach((a, i) =>        a.forEach((v, j) => {            if (v === 0) {                res += Number(dfs(i, j));            }        })    );    function dfs(i: number, j: number): boolean {        if (i < 0 || j < 0 || i >= m || j >= n) {            return false;        }        if (grid[i][j]) return true;        grid[i][j] = 1;
        return [            [i - 1, j],            [i, j + 1],            [i + 1, j],            [i, j - 1],        ]            .map((v) => dfs(v[0], v[1]))            .reduce((a, v) => a && v);    }
    return res;}export default closedIsland;