function fastSort(array) {
let left = []
let right = []
for (let i = 1i <array.lengthi++) {
if (array[i] >array[0]) right.push(array[i])
else left.push(array[i])
}
// 对两个数组进行递归再次排序直到不需要再排序（空数组或者只有一个元素的数组）
left = sortArr(left)
right = sortArr(right)
// return这两个数组以及原数组第一个元素
return [...left, ...[array[0]],...right]
}
// 数组长达大于1才进行排序否则return原数组
function sortArr(array) {
if (array.length>1)
return fastSort(array)
else return array
}
let arr = [20, 15, 14, 23, 5, 156, 245, 996, 332, 14, 52, 33, 25, 1, 45, 5, 22, 47]
let arr1 = sortArr(arr)
console.log(arr1)
// [1, 5, 5, 14, 14, 15, 20, 22, 23, 25, 33, 45, 47, 52, 156, 245, 332, 996]
求 1-100 的和
1,1,2,3,5,8,13,21,34,55,89...求第 n 项
JS 递归 假如楼梯有 n 个台阶，每次可以走 1 个或 2 个台阶，请问走完这 n 个台阶有几种走法
原理: clone(o) = new Object返回一个对象
1、很多时候可以用递归代替循环，可以理解为递归是一种特殊的循环，但通常情况下不推荐这样做。
2、递归一般是在函数里面把函数自己给调用一遍，通过每次调用改变条件，来结束循环。
3、递归在数据格式一致，在数据层级未知的情况下，比普通的遍历更有优势。
4、递归在异步的时候，更容易理解，且更容易实现，因为可以在异步的回调里面，调用自己来实现每次都能拿到异步的结果再进行其他操作。
5、递归实现的快速排序比普通遍历实现的排序效率更好。
js常用排序实现，参考代码如下
<script>Array.prototype.swap = function(i, j)
{
var temp = this[i]
this[i] = this[j]
this[j] = temp
}
Array.prototype.bubbleSort = function()
{
for (var i = this.length - 1 i > 0 --i)
{
for (var j = 0 j < i ++j)
{
if (this[j] > this[j + 1]) this.swap(j, j + 1)
}
}
}
Array.prototype.selectionSort = function()
{
for (var i = 0 i < this.length ++i)
{
var index = i
for (var j = i + 1 j < this.length ++j)
{
if (this[j] < this[index]) index = j
}
this.swap(i, index)
}
}
Array.prototype.insertionSort = function()
{
for (var i = 1 i < this.length ++i)
{
var j = i, value = this[i]
while (j > 0 && this[j - 1] > value)
{
this[j] = this[j - 1]
--j
}
this[j] = value
}
}
Array.prototype.shellSort = function()
{
for (var step = this.length >> 1 step > 0 step >>= 1)
{
for (var i = 0 i < step ++i)
{
for (var j = i + step j < this.length j += step)
{
var k = j, value = this[j]
while (k >= step && this[k - step] > value)
{
this[k] = this[k - step]
k -= step
}
this[k] = value
}
}
}
}
Array.prototype.quickSort = function(s, e)
{
if (s == null) s = 0
if (e == null) e = this.length - 1
if (s >= e) return
this.swap((s + e) >> 1, e)
var index = s - 1
for (var i = s i <= e ++i)
{
if (this[i] <= this[e]) this.swap(i, ++index)
}
this.quickSort(s, index - 1)
this.quickSort(index + 1, e)
}
Array.prototype.stackQuickSort = function()
{
var stack = [0, this.length - 1]
while (stack.length > 0)
{
var e = stack.pop(), s = stack.pop()
if (s >= e) continue
this.swap((s + e) >> 1, e)
var index = s - 1
for (var i = s i <= e ++i)
{
if (this[i] <= this[e]) this.swap(i, ++index)
}
stack.push(s, index - 1, index + 1, e)
}
}
Array.prototype.mergeSort = function(s, e, b)
{
if (s == null) s = 0
if (e == null) e = this.length - 1
if (b == null) b = new Array(this.length)
if (s >= e) return
var m = (s + e) >> 1
this.mergeSort(s, m, b)
this.mergeSort(m + 1, e, b)
for (var i = s, j = s, k = m + 1 i <= e ++i)
{
b[i] = this[(k > e || j <= m && this[j] < this[k]) ? j++ : k++]
}
for (var i = s i <= e ++i) this[i] = b[i]
}
Array.prototype.heapSort = function()
{
for (var i = 1 i < this.length ++i)
{
for (var j = i, k = (j - 1) >> 1 k >= 0 j = k, k = (k - 1) >> 1)
{
if (this[k] >= this[j]) break
this.swap(j, k)
}
}
for (var i = this.length - 1 i > 0 --i)
{
this.swap(0, i)
for (var j = 0, k = (j + 1) << 1 k <= i j = k, k = (k + 1) << 1)
{
if (k == i || this[k] < this[k - 1]) --k
if (this[k] <= this[j]) break
this.swap(j, k)
}
}
}
function generate()
{
var max = parseInt(txtMax.value), count = parseInt(txtCount.value)
if (isNaN(max) || isNaN(count))
{
alert("个数和最大值必须是一个整数")
return
}
var array = []
for (var i = 0 i < count ++i) array.push(Math.round(Math.random() * max))
txtInput.value = array.join("\n")
txtOutput.value = ""
}
function demo(type)
{
var array = txtInput.value == "" ? [] : txtInput.value.replace().split("\n")
for (var i = 0 i < array.length ++i) array[i] = parseInt(array[i])
var t1 = new Date()
eval("array." + type + "Sort()")
var t2 = new Date()
lblTime.innerText = t2.valueOf() - t1.valueOf()
txtOutput.value = array.join("\n")
}
</script>
<body onload=generate()>
<table style="width:100%height:100%font-size:12pxfont-family:宋体">
<tr>
<td align=right>
<textarea id=txtInput readonly style="width:100pxheight:100%"></textarea>
</td>
<td width=150 align=center>
随机数个数<input id=txtCount value=500 style="width:50px"><br><br>
最大随机数<input id=txtMax value=1000 style="width:50px"><br><br>
<button onclick=generate()>重新生成</button><br><br><br><br>
耗时(毫秒)：<label id=lblTime></label><br><br><br><br>
<button onclick=demo("bubble")>冒泡排序</button><br><br>
<button onclick=demo("selection")>选择排序</button><br><br>
<button onclick=demo("insertion")>插入排序</button><br><br>
<button onclick=demo("shell")>谢尔排序</button><br><br>
<button onclick=demo("quick")>快速排序(递归)</button><br><br>
<button onclick=demo("stackQuick")>快速排序(堆栈)</button><br><br>
<button onclick=demo("merge")>归并排序</button><br><br>
<button onclick=demo("heap")>堆排序</button><br><br>
</td>
<td align=left>
<textarea id=txtOutput readonly style="width:100pxheight:100%"></textarea>
</td>
</tr>
</table>
</body>
