javascript - 如何以逆时针方式循环二维数组？

Question

给定一个 m x n 维的二维数组，我如何以逆时针方式循环遍历它们？

例如:

matrix = [
  [   1,    2,   3,    4  ],
  [   5,    6,   7,    8  ],
  [   9,   10,  11,   12  ],
  [  13,   14,  15,   16  ]
]

1st loop: 1, 5, 9, 13, 14, 15, 16, 12, 8, 4, 3, 2
2nd loop: 6, 10, 11, 7, 6

我真的不介意用ruby还是js来实现

我目前的解决方案是这样的:

  (1..rotate).each do
    bottom_left_corner = i
    top_right_corner   = j
    start_nth_layer = 1; end_nth_layer = matrix.length - 2
    matrix.reverse_each do
      matrix[bottom_left_corner].unshift(matrix[bottom_left_corner - 1].shift) if bottom_left_corner > 0
      matrix[top_right_corner] << matrix[top_right_corner + 1].pop if top_right_corner < matrix.length - 1

      bottom_left_corner -= 1; top_right_corner += 1
    end

    nth_layer(matrix, start_nth_layer, end_nth_layer)

  end

更新

输出不格式化无所谓，只要输出顺序正确即可。

问题的目的

这道题的目的是逆时针遍历这些数组，逐层遍历，直到没有更多层。对于每次遍历，我们逆时针移动值。例如:

 Iteration 1:        Iteration 2:       Iteration 3:
 ==============      =============      ==============
 1    2   3   4      2   3   4   8      3   4   8  12
 5    6   7   8      1   7  11  12      2  11  10  16
 9   10  11  12  =>  5   6  10  16  =>  1   7   6  15
 13  14  15  16      9  13  14  15      5   9  13  14

Answer 1

这是矩阵层旋转问题。这是我的完整解决方案:

function matrixRotation(matrix, rotate) {
    var r = matrix.length, c = matrix[0].length;
    var depth = Math.min(r,c)/2;
    for(var i=0;i<depth;i++) {
        var x = i, y = i, n = (r-i*2 - 2)*2 + (c-i*2-2)*2+4, dir = 'down', index=0;
        var buf = [];
        while(index < n) {
            buf.push(matrix[x][y]);
            if(dir == 'down') {
                if(x+1 >= r-i) {
                    dir = 'right';
                    y++;
                } else {
                    x++;
                }
            } else if(dir == 'right') {
                if(y+1 >= c-i) {
                    dir = 'up';
                    x--;
                } else {
                    y++;
                }
            } else if(dir == 'up') {
                if(x-1 <= i-1) {
                    dir = 'left';
                    y--;
                } else {
                    x--;
                }
            } else if(dir == 'left') {
                y--;
            }
            index++;
        }
        var move = rotate%n;
        buf = [...buf.slice(buf.length-move), ...buf.slice(0, buf.length-move)]
        x = i, y = i, dir = 'down', index = 0;
        while(index < n) {
            matrix[x][y] = buf[index];
            if(dir == 'down') {
                if(x+1 >= r-i) {
                    dir = 'right';
                    y++;
                } else {
                    x++;
                }
            } else if(dir == 'right') {
                if(y+1 >= c-i) {
                    dir = 'up';
                    x--;
                } else {
                    y++;
                }
            } else if(dir == 'up') {
                if(x-1 <= i-1) {
                    dir = 'left';
                    y--;
                } else {
                    x--;
                }
            } else if(dir == 'left') {
                y--;
            }
            index++;
        }
    }
    matrix.map(row => console.log(row.join(' ')));
}

const matrix = [[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]]
// rotate count
const r = 3

matrixRotation(matrix, r);