js 实现排列组合

组合： （不考虑顺序，无重复）

//测试用例
let dataArr = [1, 2, 3, 4, 5];

function combination(dataArr, remainNum, currentArr) {
  if (remainNum === 0) {
    console.log(...currentArr);
    return;
  }
  for (let i = 0; i < dataArr.length + 1 - remainNum; i++) {
    currentArr.push(dataArr[i]);
    combination(dataArr.slice(i + 1), remainNum - 1, currentArr);
    currentArr.pop();
  }
}

const currentArr = [];
combination(dataArr, 3, currentArr);

排列：

//测试用例
let dataArr = [1, 2, 3, 4, 5];
let num = 0;

function swap(arr, m, n) {
  if (m === n) {
    return;
  }
  let temp = arr[m];
  arr[m] = arr[n];
  arr[n] = temp;
  return;
}

function fullPermutation(dataArr, index) {
  if (index === dataArr.length - 1) {
    console.log(...dataArr);
    num++;
    return;
  }
  for (let i = index; i < dataArr.length; i++) {
    swap(dataArr, index, i);
    fullPermutation(dataArr, index + 1);
    swap(dataArr, index, i);
  }
}

fullPermutation(dataArr, 0);
console.log("个数：", num);