斐波那契数列

复习->合并二维有序数组为一维数组

// flat Infinity
function a1(arr) {
  return arr.flat(Infinity).sort((a, b) => a - b);
}
// reduce
function a2(arr) {
  return arr.reduce((acc, cur) => {
    return Array.isArray(cur) ? [...acc, a2(cur)] : [...acc, cur];
  }, []);
}
// concat
function a3(arr) {
  let copyArr = [...arr];
  while (copyArr.some((item) => Array.isArray(item))) {
    copyArr = [].concat([...copyArr]);
  }
  return copyArr;
}
// 归并排序
function a4(arr) {
  function mergeSort(arr) {
    if (arr.length < 2) {
      return arr;
    }
    const middleIndex = arr >> 1;
    const left = arr.slice(0, middleIndex);
    const right = arr.slice(middleIndex);
    return merge(mergeSort(left), mergeSort(right));
  }
  function merge(left, right) {
    const result = [];
    while (left.length && right.length) {
      if (left[0] < right[0]) {
        result.push(left.shift());
      } else {
        result.push(right.shift());
      }
    }
    while (left.length) {
      result.push(left.shift());
    }
    while (right.length) {
      result.push(right.shift());
    }
    return result;
  }
  function flatten(arr) {
    return arr.reduce((pre, cur) => {
      return pre.concat(Array.isArray(cur) ? flatten(cur) : cur);
    }, []);
  }
  return mergeSort(flatten(soucreArr));
}

斐波那契 （1，1，2，3，5，8，13，21，34.。。）

function fibonacci01(n, map = {}) {
  console.log(n);
  if (n === 1 || n === 2) return 1;
  if (map[n]) return map[n];
  const data = fibonacci01(n - 1, map) + fibonacci01(n - 2, map);
  map[n] = data;
  return data;
}
function fibonacci02(n, v1 = 1, v2 = 1) {
  if (n === 1) return v1;
  if (n === 2) return v2;
  return fibonacci02(n - 1, v2, v1 + v21);
}
function fibonacci03(n) {
  let pre = 1;
  let cur = 1;
  let data;
  if (n == 1 || n == 2) return 1;
  for (let i = 3; i <= n; i++) {
    data = pre + cur;
    pre = cur;
    cur = data;
  }
  return data;
}