二维数组(matrix)翻转

以下代码为javascript中二维数组旋转变换的各种实现：

主对角线翻转（左上至右下）

const diagonal = (matrix) => {
  const len = matrix.length;
  for (let i = 0; i < len; ++i) {
    for (let j = 0; j < i; ++j) {
      const temp = matrix[i][j];
      matrix[i][j] = matrix[j][i];
      matrix[j][i] = temp;
    }
  }
};

次对角线（右上至左下）

1 2 3
4 5 6
7 8 9
[0,0] => [2,2]
[0,1] => [1,2]
[1,0] => [2,1]

// [i, j] => [len - 1 - j, len - 1 - i]
const counterDiagonal = (matrix) => {
  const len = matrix.length;
  for (let i = 0; i < len; ++i) {
    for (let j = 0; j < len - i - 1; ++j) {
      const temp = matrix[i][j];
      matrix[i][j] = matrix[len - 1 - j][len - 1 - i];
      matrix[len - 1 - j][len - 1 - i] = temp;
    }
  }
};

水平翻转（上到下）

const horizontal = (matrix) => {
  const len = matrix.length;
  for (let i = 0; i < len / 2; ++i) {
    for (let j = 0; j < len; ++j) {
      const temp = matrix[i][j];
      matrix[i][j] = matrix[len - 1 - i][j];
      matrix[len - 1 - i][j] = temp;
    }
  }
};

垂直翻转（左到右）

const vertical = (matrix) => {
  const len = matrix.length;
  for (let i = 0; i < len; ++i) {
    for (let j = 0; j < len / 2; ++j) {
      const temp = matrix[i][j];
      matrix[i][j] = matrix[i][len - 1 - j];
      matrix[i][len - 1 - j] = temp;
    }
  }
};