用荷兰国旗 改进的 快排

速记快排 时间复杂度  O(N * logN)  额外空间 O(logN)

package my_basic;

import java.util.Arrays;

import com.sun.xml.internal.bind.v2.runtime.unmarshaller.XsiNilLoader.Array;

/**
 * 用荷兰国旗改进快排
 */
public class QuickSort {
    public static void quickSort(int[] arr) {
        if (arr == null || arr.length < 2) {
            return;
        }
        quicksort(arr, 0, arr.length-1);
    }
    
    public static void quicksort (int[] arr,int l,int r) {
        if (l < r) {
            
            swap(arr, l + (int) (Math.random() * (r - l + 1)), r);   //随机快排
            int[] p = partition(arr, l, r);
            quicksort(arr, l, p[0]-1);   //经典快排每次只搞定一个  这里做了优化
            quicksort(arr, p[1]+1, r);
            
        }
        
    }
    
    public static int[] partition(int[] arr, int l, int r) {
        
        int less= l-1;
        int more = r;
        while (l < more) {
            if (arr[l] < arr[r]) {
                swap(arr, ++less, l++);
            }else if (arr[l]>arr[r]) {
                swap(arr,--more,l);
            }else {
                l++;
            }
        }
        swap(arr, more, r);
        
        return new int[] {less + 1 , more };  // =num 的左右边界
    }
    public static void swap(int[] arr, int i, int j) {
        
        int tmp = arr[i];
        arr[i]=arr[j];
        arr[j]=tmp;        
    }
    
    //对数器
    public static int[] generateRandomArray(int maxSize,int maxValue) {
        int[] arr = new int[(int) ((maxSize+1)*Math.random())];
        for (int i = 0; i < arr.length; i++) {
//            arr[i] = (int) ((maxValue+1)* Math.random() - (int)(maxValue*Math.random()));
            arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
        }
        return arr;
    }
    public static void printArray(int[] arr) {
        if (arr == null) {
            return;
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i]+" ");
        }
        System.out.println();
    }
    public static int[] copyArray(int[] arr) {
        if (arr == null) {
            return null;
        }
        int[] res = new int[arr.length];
        for (int i = 0; i < arr.length; i++) {
            res[i] = arr[i];
        }
        return res;
    }
    

    public static void comparator(int[] arr) {
        Arrays.sort(arr);        
    }
    public static boolean isEqual(int[] arr1, int[] arr2) {
        if ((arr1==null && arr2!=null) || (arr1!=null && arr2==null) ) {
            return false;
        }
        if (arr1.length != arr2.length) {
            return false;
        }
        for (int i = 0; i < arr2.length; i++) {
            if (arr1[i] != arr2[i]) {
                return false;
            }
        }
        return true;
    }
    
    public static void main(String[] args) {
        int testTime = 500000;
        int maxSize = 6;
        int maxValue = 100;
        boolean succeed = true;
        for (int i = 0; i < testTime; i++) {
            int[] arr1 = generateRandomArray(maxSize, maxValue);
            int[] arr2 = copyArray(arr1);
            quickSort(arr1);
            comparator(arr2);
            if (!isEqual(arr1, arr2)) {
                succeed = false;
                printArray(arr1);
                printArray(arr2);
                break;
            }
        }
        System.out.println(succeed ? "Nice!" : "Fucking fucked!");
    }
}