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)

  1 package my_basic;
  2 
  3 import java.util.Arrays;
  4 
  5 import com.sun.xml.internal.bind.v2.runtime.unmarshaller.XsiNilLoader.Array;
  6 
  7 /**
  8  * 用荷兰国旗改进快排
  9  */
 10 public class QuickSort {
 11     public static void quickSort(int[] arr) {
 12         if (arr == null || arr.length < 2) {
 13             return;
 14         }
 15         quicksort(arr, 0, arr.length-1);
 16     }
 17     
 18     public static void quicksort (int[] arr,int l,int r) {
 19         if (l < r) {
 20             
 21             swap(arr, l + (int) (Math.random() * (r - l + 1)), r);   //随机快排
 22             int[] p = partition(arr, l, r);
 23             quicksort(arr, l, p[0]-1);   //经典快排每次只搞定一个  这里做了优化
 24             quicksort(arr, p[1]+1, r);
 25             
 26         }
 27         
 28     }
 29     
 30     public static int[] partition(int[] arr, int l, int r) {
 31         
 32         int less= l-1;
 33         int more = r;
 34         while (l < more) {
 35             if (arr[l] < arr[r]) {
 36                 swap(arr, ++less, l++);
 37             }else if (arr[l]>arr[r]) {
 38                 swap(arr,--more,l);
 39             }else {
 40                 l++;
 41             }
 42         }
 43         swap(arr, more, r);
 44         
 45         return new int[] {less + 1 , more };  // =num 的左右边界
 46     }
 47     public static void swap(int[] arr, int i, int j) {
 48         
 49         int tmp = arr[i];
 50         arr[i]=arr[j];
 51         arr[j]=tmp;        
 52     }
 53     
 54     //对数器
 55     public static int[] generateRandomArray(int maxSize,int maxValue) {
 56         int[] arr = new int[(int) ((maxSize+1)*Math.random())];
 57         for (int i = 0; i < arr.length; i++) {
 58 //            arr[i] = (int) ((maxValue+1)* Math.random() - (int)(maxValue*Math.random()));
 59             arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random());
 60         }
 61         return arr;
 62     }
 63     public static void printArray(int[] arr) {
 64         if (arr == null) {
 65             return;
 66         }
 67         for (int i = 0; i < arr.length; i++) {
 68             System.out.print(arr[i]+" ");
 69         }
 70         System.out.println();
 71     }
 72     public static int[] copyArray(int[] arr) {
 73         if (arr == null) {
 74             return null;
 75         }
 76         int[] res = new int[arr.length];
 77         for (int i = 0; i < arr.length; i++) {
 78             res[i] = arr[i];
 79         }
 80         return res;
 81     }
 82     
 83 
 84     public static void comparator(int[] arr) {
 85         Arrays.sort(arr);        
 86     }
 87     public static boolean isEqual(int[] arr1, int[] arr2) {
 88         if ((arr1==null && arr2!=null) || (arr1!=null && arr2==null) ) {
 89             return false;
 90         }
 91         if (arr1.length != arr2.length) {
 92             return false;
 93         }
 94         for (int i = 0; i < arr2.length; i++) {
 95             if (arr1[i] != arr2[i]) {
 96                 return false;
 97             }
 98         }
 99         return true;
100     }
101     
102     public static void main(String[] args) {
103         int testTime = 500000;
104         int maxSize = 6;
105         int maxValue = 100;
106         boolean succeed = true;
107         for (int i = 0; i < testTime; i++) {
108             int[] arr1 = generateRandomArray(maxSize, maxValue);
109             int[] arr2 = copyArray(arr1);
110             quickSort(arr1);
111             comparator(arr2);
112             if (!isEqual(arr1, arr2)) {
113                 succeed = false;
114                 printArray(arr1);
115                 printArray(arr2);
116                 break;
117             }
118         }
119         System.out.println(succeed ? "Nice!" : "Fucking fucked!");
120     }
121 }

标签：国旗,return,int,arr,快排,static,arr2,荷兰,public
来源： https://www.cnblogs.com/lihuazhu/p/10753172.html