排列组合矩阵实现 about logic-training

[bq-hentai]

/** [1, 2] [3, 4, 5] [6, 7, 8] */

function gen (...xss) {
  const len = xss.length
  const ret = []

  if (len === 0) {
    return ret
  }

  function genCore (acc, xssIndex) {
    const xs = xss[xssIndex]
    if (xs.length !== 0) {
      xs.forEach((x, i) => {
        const newAcc = [...acc, x]
        if (xssIndex + 1 === len) {
          ret.push(newAcc)
          return
        }
        genCore(newAcc, xssIndex + 1)
      })
      return
    }
    genCore(acc, xssIndex + 1)
  }

  genCore([], 0)
  return ret
}

function test (...xs) {
  console.time('gen')
  const ret = gen(...xs)
  console.timeEnd('gen')
  return ret
}

test([1, 2, 3, 4, 5], [1, 2, 3, 4, 5], [6, 7, 8, 9, 10])

爽不爽

[erbing]

function cartesian (...lists) {
  return lists
    .map(list => list.map(item => [item]))
    .reduce((listsA, listsB) =>
      listsA.reduce((list, listA) =>
        list.concat(
          listsB.map(listB => listA.concat(listB))
        ), []
      )
    )
}