在javascript中交换矩阵的列（换位）

Question

例如，我有一个像这样的矩阵：|1 2 3|    |4 5 6||7 8 9|我需要它转换成这样的矩阵：|1 4 7|    |2 5 8||3 6 9|实现这一目标的最佳和最佳方式是什么？

Answer 1

参见文章：在JavaScript和jQuery中转置数组

function transpose(a) {

  // Calculate the width and height of the Array

  var w = a.length || 0;

  var h = a[0] instanceof Array ? a[0].length : 0;

  // In case it is a zero matrix, no transpose routine needed.

  if(h === 0 || w === 0) { return []; }

  /**

   * @var {Number} i Counter

   * @var {Number} j Counter

   * @var {Array} t Transposed data is stored in this array.

   */

  var i, j, t = [];

  // Loop through every item in the outer array (height)

  for(i=0; i<h; i++) {

    // Insert a new row (array)

    t[i] = [];

    // Loop through every item per item in outer array (width)

    for(j=0; j<w; j++) {

      // Save transposed data.

      t[i][j] = a[j][i];

    }

  }

  return t;

}

console.log(transpose([[1,2,3],[4,5,6],[7,8,9]]));

Answer 2

DuckDucking打开了这个由肯。令人惊讶的是，它比尼基塔的答案更加简洁和完整。它在内核中隐式检索列和行长度map()。

function transpose(a) {

    return Object.keys(a[0]).map(function(c) {

        return a.map(function(r) { return r[c]; });

    });

}

console.log(transpose([

    [1,2,3],

    [4,5,6],

    [7,8,9]

]));

Answer 3

就像任何其他语言一样：

int[][] copy = new int[columns][rows];

for (int i = 0; i < rows; ++i) {

    for (int j = 0; j < columns; ++j) {

        copy[j][i] = original[i][j];

    }

}

您只需在JS中以不同方式构造2D数组。像这样：

function transpose(original) {

    var copy = [];

    for (var i = 0; i < original.length; ++i) {

        for (var j = 0; j < original[i].length; ++j) {

            // skip undefined values to preserve sparse array

            if (original[i][j] === undefined) continue;

            // create row if it doesn't exist yet

            if (copy[j] === undefined) copy[j] = [];

            // swap the x and y coords for the copy

            copy[j][i] = original[i][j];

        }

    }

    return copy;

}

console.log(transpose([

    [1,2,3],

    [4,5,6],

    [7,8,9]

]));