js排序之快速排序

function quickSort(arr) {
	var len = arr.length
	if (len <= 1) {
		return arr
	}
	let leftArr = []
	let rightArr = []
	let pivotIndex = Math.floor(arr.length / 2);
	var pivot = arr.splice(pivotIndex, 1)[0]
	for (let i = 0; i < len - 1; i++) {
		if (arr[i] < pivot) {
			leftArr.push(arr[i])
		} else {
			rightArr.push(arr[i])
		}
	}
	return quickSort(leftArr).concat([pivot], quickSort(rightArr))
}
var arr = [1, 3, 5, 7, 8, 6, 4, 2]
console.log(quickSort(arr)) //[1,2,3,4,5,6,7,8]

//es6实现快速排序

function quickSort(arr){
	if(!arr.length){
		return []
	}
	const [pivot,...rest] = arr
	return [...quickSort(rest.filter(item=>item<pivot)),pivot,...quickSort(rest.filter(item=>item>=pivot))]
}
var arr = [7,9,5,2,4,3,1,8]
console.log(quickSort(arr)) //[1,2,3,4,5,6,7,8] ES6,真香！