标签：style blog color io os 使用 java ar for
参考资料：算法导论
note1:桶排序是另外一种以O(n)或者接近O(n)的复杂度排序的算法. 它假设输入的待排序元素是等可能的落在等间隔的值区间内.一个长度为N的数组使用桶排序, 需要长度为N的辅助数组. 等间隔的区间称为桶, 每个桶内落在该区间的元素. 桶排序是基数排序的一种归纳结果
note2:待排序元素越均匀, 桶排序的效率越高. 均匀意味着每个桶在中间过程中容纳的元素个数都差不多,不会出现特别少或者特别多的情况, 这样在排序子程序进行桶内排序的过程中会达到最优效率.
note3:将元素通过恰当的映射关系将元素尽量等数量的分到各个桶(值区间)里面, 这个映射关系就是桶排序算法的关键.桶的标记(数组索引Index)的大小也要和值区间有对应关系
代码：
1 package sorts; 2 3 import java.util.Arrays; 4 import java.util.Random; 5 6 class Bucket { 7 private double data; 8 private Bucket next; 9 public double getData() { 10 return data; 11 } 12 public void setData(double data) { 13 this.data = data; 14 } 15 public Bucket getNext() { 16 return next; 17 } 18 public void setNext(Bucket next) { 19 this.next = next; 20 } 21 @Override 22 public String toString() { 23 return Double.toString(data); 24 } 25 } 26 27 public class BucketSort { 28 29 /** 30 * Input element MUST be in the range [0, 1). Or 31 * the program may not function properly. 32 * */ 33 public static void sort(double[] a) { 34 // init 35 Bucket[] buckets = new Bucket[a.length]; 36 int n = a.length; 37 // sort 38 for (int i = 0; i < a.length; i++) { 39 addBucket(buckets, (int)(a[i] * n), a[i]); 40 } 41 retrieveBuckets(buckets, a); 42 } 43 44 private static void retrieveBuckets(Bucket[] buckets, double[] a) { 45 Bucket iterator = null; 46 int index = 0; 47 for (int i = 0; i < buckets.length; i++) { 48 iterator = buckets[i]; 49 while (iterator!=null) { 50 a[index++] = iterator.getData(); 51 iterator = iterator.getNext(); 52 } 53 } 54 } 55 56 // no need for insertion sort 57 private static void addBucket(Bucket[] buckets, int index, double data) { 58 Bucket iterator = buckets[index]; 59 if (iterator == null) { 60 Bucket tmp = new Bucket(); 61 tmp.setData(data); 62 tmp.setNext(buckets[index]); 63 buckets[index] = tmp; 64 } else { 65 Bucket tmp = new Bucket(); 66 Bucket previous = iterator; 67 tmp.setData(data); 68 while ((iterator!=null) && 69 (data > iterator.getData())) { 70 previous = iterator; 71 iterator = iterator.getNext(); 72 } 73 if (iterator==previous) { 74 tmp.setNext(iterator.getNext()); 75 iterator.setNext(tmp); 76 } else { 77 previous.setNext(tmp); 78 tmp.setNext(iterator); 79 } 80 } 81 } 82 83 // test 84 public static void main(String[] args) { 85 Random random = new Random(); 86 int num = 10; 87 double[] a = new double[num]; 88 for (int i = 0; i < num; i++) { 89 a[i] = random.nextDouble(); 90 } 91 BucketSort.sort(a); 92 System.out.println(Arrays.toString(a)); 93 } 94 95 }
标签：style blog color io os 使用 java ar for
原文地址：http://www.cnblogs.com/qrlozte/p/3969973.html
