数组全排列

var arr = [["1","2"],["3","4","5"]]; 预期结果 [["1","3"],["1","4"],["1","5"],["2","3"],["2","4"],["2","5"]]

其实这有点像手机的 9 宫格输入法，去算笛卡尔积。

//递归法
const arr = [["1", "2"], ["3", "4", "5"]];
function permuteA(arr) {
  if (arr.length === 0) {
    return [[]];
  }
  const result = [];
  const rest = permute(arr.slice(1));
  for (let i = 0; i < rest.length; i++) {
    for (let j = 0; j < arr[0].length; j++) {
      result.push([arr[0][j], ...rest[i]]);
} }
  return result;
}
    const result = permuteA(arr); console.log('递归结果====>:', result);

//迭代法
const arr = [["1", "2"], ["3", "4", "5"]];
function permuteB(arr) {
  if (arr.length === 0) {
    return [[]];
  }
  let result = [[]];
  for (let i = 0; i < arr.length; i++) {
    const newResult = [];
    for (let j = 0; j < result.length; j++) {
      for (let k = 0; k < arr[i].length; k++) {
        newResult.push([...result[j], arr[i][k]]);
} }
    result = newResult;
  }
  return result;
}
const result = permuteB(arr); console.log('迭代结果====>:',result);