快速排序的原理：每次将序列以一个值为界限分成两组，在将两个序列分别以一个界限分成两组这样一直分下去。
int[] a = {11,222,44,63,84,11,24,53,123,25,98,76,34};
第一步：以34将数组a分成两组 11, 25, 24, 11 34, 63, 44, 53, 123, 222, 98, 76, 84
第二步：以11将11, 25, 24, 11分为两组 11, 11, 24, 25。以84将34, 63, 44, 53, 123, 222, 98, 76, 84分为两组34, 63, 44, 53, 76, 84 98, 123, 222。
这样一直循环下去直到不能再分。
import java.util.Arrays;
public class QuickSort {
public static int partition(int[] arrays,int left,int right){
int leftPart = left -1;
int rightPart = right;
//拿出数组最后一个词作为界限，数组的最后一个本身不参与比较
int median = arrays[right];
while(true){
while(leftPart < rightPart && arrays[++leftPart] <= median);
while(leftPart < rightPart && arrays[--rightPart] >= median);
if(leftPart >= rightPart){
break;
}else{
change(arrays,leftPart,rightPart);
}
}
//将界限的值也就是数组最后一个放到两组的中间
change(arrays,leftPart,right);
System.out.println(Arrays.toString(arrays));
return leftPart;
}
public static void quickSort(int[] arrays,int left,int right){
if(left >= right){
return;
}else{
int partition = partition(arrays, left, right);
//分别在递归排序两个组，中间的界限不参与。
quickSort(arrays,left,partition-1);
quickSort(arrays,partition+1,right);
}
}
public static void change(int[] arrays,int left,int right){
int temp = arrays[left];
arrays[left] = arrays[right];
arrays[right] = temp;
}
public static void main(String[] args) {
int[] a = {11,222,44,63,84,11,24,53,123,25,98,76,34};
quickSort(a, 0,a.length-1);
System.out.println(Arrays.toString(a));
}
}