如何在 Javascript 中进行排列？

Question

我想用 javascript 进行排列，这是我的代码

const arr = [1, 2, 3, 4, 5];

for (let i1 = 0; i1 < arr.length; i1++) {

  for (let i2 = i1 + 1; i2 < arr.length; i2++) {

    console.log(arr[i1] + ' ' + arr[i2]);

  }

}

https://jsfiddle.net/op51x6mv/1/

该代码的结果：

["1 2", "1 3", "1 4", "1 5", "2 3", "2 4", "2 5", "3 4", "3 5", "4 5"]

我想问，为什么排列的所有结果都没有显示出来？从这些结果中我没有看到数字

["2 1", "3 1", "3 2", "4 1", "4 2", "4 3", "5 1", "5 2", "5 3", "5 4"]

请告诉我这段代码的错误在哪里？或者，如果您有更好的代码，请帮助我。

谢谢

Answer 1

您可以从头到尾循环两次并省略相同的索引。const arr = [1, 2, 3, 4, 5];for (let i1 = 0; i1 < arr.length; i1++) {&nbsp; &nbsp; for (let i2 = 0; i2 < arr.length; i2++) {&nbsp; &nbsp; &nbsp; &nbsp; if (i1 === i2) continue;&nbsp; &nbsp; &nbsp; &nbsp; console.log(arr[i1] + ' ' + arr[i2]);&nbsp; &nbsp; }}

Answer 2

你想要的是......在数学上......不是排列，而是没有重复的变化（但这实际上是无关紧要的）。我早些时候在 PHP 中为此编写了一个代码，这是它的 JS 变体（选择给定数量的元素，可以处理数据中的重复等）：const variations = (arr, n = arr.length) => {&nbsp; if(n === 0) return [[]]&nbsp; if(!(n >= 0)) return []&nbsp; const output = []&nbsp; for(let i = 0; i < arr.length; i++){&nbsp; &nbsp; if(arr.indexOf(arr[i]) < i) continue&nbsp; &nbsp; const newArr = arr.slice()&nbsp; &nbsp; newArr.splice(i, 1)&nbsp; &nbsp; output.push(...variations(newArr, n - 1).map(e => [arr[i], ...e]))&nbsp; }&nbsp; return output}const arr = [1, 2, 3, 4, 5];console.log(variations(arr, 2))//If you want to concatenate them, use:console.log(variations(arr, 2).map(e => e.join(' ')))

Answer 3

const arr = [1, 2, 3, 4, 5];for (let i = 0; i < arr.length; i++) {&nbsp; for (let j = 0; j < arr.length; j++) {&nbsp; &nbsp; &nbsp; if (i === j) continue;&nbsp; &nbsp; &nbsp; console.log(arr[i] + ' ' + arr[j]);&nbsp; }}