桶式 基数排序

import java.util.Arrays;public class Sort {// 桶式排序// 桶式排序不再是基于比较的了，它和基数排序同属于分配类的排序.// 桶式排序事先要知道待排序列在一个范围内，而且这个范围应该不是很大的。// 比如知道待排序列在[0,M）内，那么可以分配M个桶，第I个桶记录I的出现情况，最后根据// 每个桶收到的位置信息把数据输出成有序的形式。// 这里我们用两个临时性数组，一个用于记录位置信息，一个用于方便输出数据成有序方式，// 另外我们假设数据落在0到MAX,如果所给数据不是从0开始，可以把每个数减去最小的数。public static void bucketSort(int[] keys, int from, int len, int max) {int[] tmp = new int[len];int[] count = new int[max];for (int i = 0; i < len; i++)count[keys[from + i]]++;for (int i = 1; i < max; i++)count[i] = count[i] + count[i - 1];// this means how many number// which is less or equals than// i,thus it is also position +1System.arraycopy(keys, from, tmp, 0, len);for (int k = len - 1; k >= 0; k--)// from the ending to beginning can// keep the stability// position +1 =countkeys[--count[tmp[k]]] = tmp[k];}public static boolean USE_LINK = true;// 基数排序可以说是扩展了的桶式排序，比如当待排序列在一个很大的范围内，比如0到999999内，// 那么用桶式排序是很浪费空间的。而基数排序把每个排序码拆成由d个排序码，比如任何一个6位数// （不满六位前面补0）拆成6个排序码，分别是个位的，十位的，百位的。。。。// 排序时，分6次完成，每次按第i个排序码来排。// 一般有两种方式:// 1) 高位优先(MSD)： 从高位到低位依次对序列排序// 2）低位优先(LSD)： 从低位到高位依次对序列排序// 计算机一般采用低位优先法（人类一般使用高位优先），但是采用低位优先时要确保排序算法的稳定性。// 基数排序借助桶式排序，每次按第N位排序时，采用桶式排序。对于如何安排每次落入同一个桶中// 的数据有两种安排方法：// 1）顺序存储：每次使用桶式排序，放入r个桶中，，相同时增加计数。// 2）链式存储：每个桶通过一个静态队列来跟踪。public static void RadixSort(int[] keys, int from, int len, int radix, int d) {if (USE_LINK)link_radix_sort(keys, from, len, radix, d);elsearray_radix_sort(keys, from, len, radix, d);}private static void array_radix_sort(int[] keys, int from, int len,int radix, int d) {int[] tmpArray = new int[len];int[] count = new int[radix];int R = 1;for (int i = 0; i < d; i++) {System.arraycopy(keys, from, tmpArray, 0, len);Arrays.fill(count, 0);for (int j = 0; j < len; j++) {int subkey = (tmpArray[j] / R) % radix;count[subkey]++;}for (int j = 1; j < radix; j++)count[j] = count[j] + count[j - 1];for (int m = len - 1; m >= 0; m--) {int subKey = (tmpArray[m] / R) % radix;--count[subKey];keys[from + count[subKey]] = tmpArray[m];}R *= radix;}}private static class LinkQueue {int head = -1;int tail = -1;}private static void link_radix_sort(int[] keys, int from, int len,int radix, int d) {int[] nexts = new int[len];LinkQueue[] queues = new LinkQueue[radix];for (int i = 0; i < radix; i++)queues[i] = new LinkQueue();for (int i = 0; i < len - 1; i++)nexts[i] = i + 1;nexts[len - 1] = -1;int first = 0;for (int i = 0; i < d; i++) {link_radix_sort_distribute(keys, from, len, radix, i, nexts,queues, first);first = link_radix_sort_collect(keys, from, len, radix, i, nexts,queues);}int[] tmps = new int[len];int k = 0;while (first != -1) {tmps[k++] = keys[from + first];first = nexts[first];}System.arraycopy(tmps, 0, keys, from, len);}private final static void link_radix_sort_distribute(int[] keys, int from,int len, int radix, int d, int[] nexts, LinkQueue[] queues,int first) {for (int i = 0; i < radix; i++)queues[i].head = queues[i].tail = -1;while (first != -1) {int val = keys[from + first];for (int j = 0; j < d; j++)val /= radix;val = val % radix;if (queues[val].head == -1) {queues[val].head = first;} else {nexts[queues[val].tail] = first;}queues[val].tail = first;first = nexts[first];}}private static int link_radix_sort_collect(int[] keys, int from, int len,int radix, int d, int[] nexts, LinkQueue[] queues) {int first = 0;int last = 0;int fromQueue = 0;for (; (fromQueue < radix - 1) && (queues[fromQueue].head == -1); fromQueue++);first = queues[fromQueue].head;last = queues[fromQueue].tail;while (fromQueue < radix - 1 && queues[fromQueue].head != -1) {fromQueue += 1;for (; (fromQueue < radix - 1) && (queues[fromQueue].head == -1); fromQueue++);nexts[last] = queues[fromQueue].head;last = queues[fromQueue].tail;}if (last != -1)nexts[last] = -1;return first;}public static void main(String[] args) {int[] a = { 1, 4, 8, 3, 2, 9, 5, 0, 7, 6, 9, 10, 9, 13, 14, 15, 11, 12,17, 16 };bucketSort(a, 0, a.length, 22);for (int i = 0; i < a.length; i++)System.out.print(a[i] + " ");System.out.println("");int[] b = { 1, 4, 8, 3, 2, 9, 5, 0, 7, 6, 9, 10, 9, 135, 14, 15, 11,5576, 467676, 12, 17, 45, 16 };USE_LINK = true;RadixSort(b, 0, b.length, 10, 10);for (int i = 0; i < b.length; i++)System.out.print(b[i] + " ");}}

 来自：http://www.blogjava.net/javacap/archive/2007/12/14/167618.html