script.html

<script code-main>
    /********** 基础版 **********/
    function eightQueens(row, length, matrix) {
        if (row > length - 1) {
            printResult(matrix);
            return;
        }

        for (let column = 0; column < length; ++column) {
            if (checkQueen(row, column, length, matrix)) {
                matrix[row][column] = 1;
                eightQueens(row + 1, length, matrix);
                matrix[row][column] = 0;
            }
        }
    }

    let resultCount = 0;

    function printResult(matrix) {
        console.log(`result no: ${++resultCount}\r\n` + matrix.map(row => row.join(', ')).join('\r\n'));
    }

    function checkQueen(row, column, length, matrix) {
        for (let i = 0; i < length; ++i) {
            if (i !== column && matrix[row][i]) {
                return false;
            }
            if (i !== row && matrix[i][column]) {
                return false;
            }
        }

        for (let i = 0; i < length; ++i) {
            if (i !== row) {
                const diff = i - row;

                if (column - diff >= 0 && column - diff < length && matrix[i][column - diff]) {
                    return false;
                }
                if (column + diff >= 0 && column + diff < length && matrix[i][column + diff]) {
                    return false;
                }
            }
        }

        return true;
    }

    const matrix = [
        [0, 0, 0, 0, 0, 0, 0, 0, ],
        [0, 0, 0, 0, 0, 0, 0, 0, ],
        [0, 0, 0, 0, 0, 0, 0, 0, ],
        [0, 0, 0, 0, 0, 0, 0, 0, ],
        [0, 0, 0, 0, 0, 0, 0, 0, ],
        [0, 0, 0, 0, 0, 0, 0, 0, ],
        [0, 0, 0, 0, 0, 0, 0, 0, ],
        [0, 0, 0, 0, 0, 0, 0, 0, ],
    ];

    eightQueens(0, 8, matrix);

    /********** 标记优化版 **********/
    let resultCount2 = 0;

    function eightQueens2(row, length, signCol, signLeft, signRight) {
        if (row >= length) {
            ++resultCount2;
            return;
        }

        for (let column = 0; column < length; ++column) {
            if (checkQueen2(row, column, signCol, signLeft, signRight)) {
                setQueen(row, column, signCol, signLeft, signRight);
                eightQueens2(row + 1, length, signCol, signLeft, signRight);
                deleteQueen(row, column, signCol, signLeft, signRight);
            }
        }
    }

    function checkQueen2(row, column, signCol, signLeft, signRight) {
        if (signCol[column]) {
            return false;
        }
        if (signLeft[row + column]) {
            return false;
        }
        if (signRight[row - column]) {
            return false;
        }
        return true;
    }

    function setQueen(row, column, signCol, signLeft, signRight) {
        signCol[column] = 1;
        signLeft[row + column] = 1;
        signRight[row - column] = 1;
    }

    function deleteQueen(row, column, signCol, signLeft, signRight) {
        signCol[column] = 0;
        signLeft[row + column] = 0;
        signRight[row - column] = 0;
    }

    eightQueens2(0, 8, {}, {}, {}, {});

    console.log('count2:', resultCount2);
</script>