JavaScript algorithm series of fast Sorting (Quicksort) algorithm examples of detailed _javascript skills

The idea of "quick sort" is simple, and the whole sort process takes only three steps:

(1) In the dataset, select an element as the "datum" (pivot).

(2) All elements less than "datum" are moved to the left of the datum, and all elements greater than "datum" are moved to the right side of the datum.

(3) for the two subsets to the left and right of the "datum", repeat the first and second steps until all subsets are left with only one element.

For example, now there is a dataset {85, 24, 63, 45, 17, 31, 96, 50}, how do you sort it?

The first step is to select the middle element 45 as the "benchmark". (Datum values can be selected arbitrarily, but it is easier to understand the median value.) ）

In the second step, each element is compared to the "datum" in order to form two subsets, one "less than 45" and the other "greater than or equal to 45".

In the third step, repeat the first and second steps for the two subsets until all subsets are left with only one element.

The following reference to the online data (here and here), using JavaScript language to implement the above algorithm.

First, define a quicksort function, whose argument is an array.

var quickSort = function (arr) {
};

Then, check the number of elements in the array and return if it is less than or equal to 1.

var quickSort = function (arr) {
if (arr.length <= 1) {return arr;}
};

Next, select "Datum" (pivot) and separate it from the original array, then define two empty arrays to hold two subsets of the left and right.

var quickSort = function (arr) {
if (arr.length <= 1) {return arr;}
var pivotindex = Math.floor (ARR.LENGTH/2);
var pivot = Arr.splice (pivotindex, 1) [0];
var left = [];
var right = [];
};

Then, start traversing the array, less than the elements of "datum" into the left subset, and the elements larger than the datum into the right subset.

var quickSort = function (arr) {
if (arr.length <= 1) {return arr;}
var pivotindex = Math.floor (ARR.LENGTH/2);
var pivot = Arr.splice (pivotindex, 1) [0];
var left = [];
var right = [];
for (var i = 0; i < arr.length i++) {
if (Arr[i] < pivot) {
Left.push (arr[i));
else {
Right.push (arr[i]);
}
}
;

Finally, using recursion to repeat the process, you can get the sorted array.

var quickSort = function (arr) {
if (arr.length <= 1) {return arr;}
var pivotindex = Math.floor (ARR.LENGTH/2);
var pivot = Arr.splice (pivotindex, 1) [0];
var left = [];
var right = [];
for (var i = 0; i < arr.length i++) {
if (Arr[i] < pivot) {
Left.push (arr[i));
else {
Right.push (arr[i]);
}
return
QuickSort (left). Concat ([pivot], quickSort (right);
};

When used, direct call to Quicksort () on the line.

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