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export default function solveNQueens(n: number): string[][] {    if (n === 1) return [["Q"]];    if (n === 2 || n === 3) return [];    const solutions: string[][] = [];
    permute_index(        Array.from({ length: n }).map((_v, i) => i),        (indexs: number[]) => {            if (check_that_the_slashes_are_conflicting(indexs)) {                return;            }            const s = indexs.map((v) => {                const line: string[] = [];                line.length = n;                line.fill(".");                line[v] = "Q";                return line.join("");            });            solutions.push(s);        },    );    return solutions;}function check_that_the_slashes_are_conflicting(indexs: number[]): boolean {    const diagonals1 = new Set<number>();    const diagonals2 = new Set<number>();    for (const [row, column] of indexs.entries()) {        const diagonal1 = row - column;        if (diagonals1.has(diagonal1)) {            return true;        }        const diagonal2 = row + column;        if (diagonals2.has(diagonal2)) {            return true;        }        diagonals1.add(diagonal1);        diagonals2.add(diagonal2);    }    return false;}function permute_index(nums: number[], output: (indexs: number[]) => void) {    const k = nums.length;    if (k === 0) {        return;    }    if (k === 1) {        output([0].map((v) => nums[v]));        return;    }
    permute_index(nums.slice(0, -1), (indexs) => {        const arrays: number[][] = [];        for (let i = 0; i < indexs.length + 1; i++) {            const b = Array.from(indexs);            b.splice(i, 0, nums.slice(-1)[0]);            arrays.push(b);        }
        for (const res of arrays) {            output(res);        }    });}