合并二维有序数组成一维有序数组，归并排序的思路

昨日回顾

自己做定时器，间隔时间是 a, a+b a+2b...a+nb

function myIntervalFn(fn, a, b) {
  this.a = a;
  this.b = b;
  this.time = 0;
  this.timer = null;
  this.start = () => {
    this.timer = setTimeout(() => {
      fn();
      this.start();
      this.time++;
    }, a + this.time * this.b);
  };
  this.stop = function() {
    if (this.timer) {
      clearTimeout(this.timer);
      this.time = 0;
    }
  };
}
function aa() {
  console.log(111);
}
const a = new myIntervalFn(aa, 1000, 2000);
a.start();
setTimeout(function() {
  a.stop();
}, 10000);

今日份解题

const soucreArr = [
  [1, 21, 123, 12],
  [11, 23, 12, 123],
  [543, 652, 5, 7, 78],
];
/// 方法一： flat
function myFlatSort(arr) {
  return [...new Set(soucreArr.flat(Infinity).sort((a, b) => a - b))];
}
/// 方法二： concat
function myConncat(arr) {
  let copyArr = [...arr];
  while (copyArr.some((item) => Array.isArray(item))) {
    copyArr = [].concat(...copyArr);
    console.log(copyArr);
  }
  return copyArr;
}
/// 方法三：reduce
function myReduce(arr) {
  const arrCopy = arr.reduce((acc, cur) => {
    return Array.isArray(cur) ? [...acc, ...myReduce(cur)] : [...acc, cur];
  }, []);
  return arrCopy;
}
/// 方法四：
// 排序一个数组，先把数组从中间分成前后两部分，然后对前后两部分分别排序，再将排序好的两部分合并到一起，这样整个数组就有序了
/// 归并排序采用的是分治思想
function mergeSort(arr) {
  const len = arr.length;
  if (len < 2) return arr;
  const middleIndex = len >> 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]) {
      /// 类似队列的队首出队
      result.push(left.shift());
    } else {
      result.push(right.shift());
    }
  }
  /// 如果还有剩余元素，直接从头到尾放到数组尾部
  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);
  }, []);
}
mergeSort(flatten(soucreArr));