为什么 JS 中写第一种快排比标准快排慢 3 倍？

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这是一个创建于 1024 天前的主题，其中的信息可能已经有所发展或是发生改变。

自己学习算法，根据快排的定义实现了，但发现比标准的快排写法慢 3 倍，求高手指点一二

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/*
1. 终止条件 若数组只有 1 个了，那么返回第一个
2. 取基数，拿第一个
3. 从第二个开始遍历，并比较，小的放左数组，大的放右数组，递归
*/

var quickSort = originArr => {
  if(originArr.length <= 0) return 
  var baseNum = originArr[0]
  var leftArr = []
  var rightArr = []
  originArr.forEach( (item,index) => {
    if(index !== 0) {
          item > baseNum ? rightArr.push(item) : leftArr.push(item)
    }

  })

  var left = leftArr.length>=1 ? quickSort(leftArr):[]
  var right = rightArr.length>=1 ?quickSort(rightArr):[]

  return [...left, baseNum, ...right]
}
console.time()
// var s = quickSort(origin)
var s = quickSort(c)
console.timeEnd()
// console.log(s)

console.time()
var b = _quickSort(c,0,c.length-1)
console.timeEnd()
// console.log(b)

function _quickSort(arr, left, right) {
  if (left < right) {
    var pivot = arr[right];
    var i = left,
      j = right - 1;

    while (true) {
      
      while (arr[i] < pivot && i < right) i++;
     
      while (arr[j] >= pivot && j > i) j--;
       
      if (i >= j) {
        break;
      }
      swap(arr, i, j);
    }

    var mid = j;

    if(i !== right){ 
      swap(arr, j, right);
    } else{
      mid = right
    }

    _quickSort(arr, left, mid - 1);
    _quickSort(arr, mid + 1, right);
  }
}

12 条回复 • 2022-03-01 10:45:46 +08:00