A quick sort of Java sorting algorithm

Basic Process:

1. Set two variables i, j, when the sort begins: i=0,j=n-1;
2. With the first array element as the key data, assign a value to key , i.e. key =a[0];
3. Search forward from j, that is, after starting the forward search (j--), find the first value less than key a[j], will a[j] and a[i] interchange;
4. From I start backward search, that is, start backward search (i++), find the first a[i] greater than key ], will a[i] and a[j] interchange;
5. repeat 3rd, 4, until i=j, (3,4 step, did not find the qualifying value, that is, 3 a[j] is not less than key, 4 a[i] is not larger than the time of key change j, i value, make j=j-1, i=i+1 until it is found).

Code implementation:

 public classKuaisu { public Static voidmain (String []args) {int[] A = {12,20,5,16,15,1,30,45,23,9}; intLow = 0; intHigh = A.length-1;        Paixu (a,low,high);  for(inti = 0; i<a.length; i++) {System.out.print (a[i]+","); }          }         public Static voidPaixu (int[] a,intLowinthigh ) {        if(low<high ) {            intKey =Sort (a,low,high); Paixu (a,low,key-1); Paixu (a,key+1, high); }    }               public Static intSortint[] a,intLowinthigh ) {         intKey =a[low];  while(high>low ) {             //compare from backward to forward              while(high>low&&a[high]>=key) {//if it is larger than the key move positionhigh--; } a[low]=a[high];//not greater than, Exchange two values//from the Post-trip comparison              while(high>low&&a[low]<=key) {//if less than key move positionlow++; } a[high]=a[low];//no less than, exchange two values} a[low]=key; returnlow ; }}

Algorithm Performance Analysis:

Time complexity: fast sorting the worst time complexity is O (n^2), and the average time complexity is O (nlogn).

Space Complexity: O (n).

Stability: Direct selection is an unstable sort method because there is an interchange between nonadjacent elements in the direct selection Sort.

A quick sort of Java sorting algorithm