介绍

排列（英语：Permutation，置换）是将相异物件或符号根据确定的顺序重排。每个顺序都称作一个排列。例如，从一到六的数字有 720 种排列，对应于由这些数字组成的所有不重复亦不阙漏的序列，例如 "4, 5, 6, 1, 2, 3" 与 1, 3, 5, 2, 4, 6。

实现

JavaScript

/*
a permutation of a set is, loosely speaking, an arrangement of its members into a sequence or linear order, or if the set is already ordered, a rearrangement of its elements.
The word "permutation" also refers to the act or process of changing the linear order of an ordered set
More at : https://en.wikipedia.org/wiki/Permutation
*/

const createPermutations = (str) => {
 // convert string to array
 const arr = str.split("");

 // get array length
 const strLen = arr.length;
 // this will hold all the permutations
 const perms = [];
 let rest;
 let picked;
 let restPerms;
 let next;

 // if strLen is zero, return the same string
 if (strLen === 0) {
  return [str];
 }
 // loop to the length to get all permutations
 for (let i = 0; i < strLen; i++) {
  rest = Object.create(arr);
  picked = rest.splice(i, 1);

  restPerms = createPermutations(rest.join(""));

  for (let j = 0, jLen = restPerms.length; j < jLen; j++) {
   next = picked.concat(restPerms[j]);
   perms.push(next.join(""));
  }
 }
 return perms;
};

• Object.create() (opens new window) 方法用于创建一个新对象，使用现有的对象来作为新创建对象的原型（prototype）。参见：Object.create ()、new Object () 和 {} 的区别 - 掘金 (opens new window)。
• splice() (opens new window) 方法通过删除或替换现有元素或者原地添加新的元素来修改数组，并以数组形式返回被修改的内容。此方法会改变原数组。

参考

• Permutation - Wikiwand (opens new window)