排序算法——基数排序（Radix sort）【代码实现】

C

#include <stdio.h>
#include <limits.h>
#include <stdlib.h>
#include <time.h>
 
// Get size of statically allocated array
#define ARR_LEN(ARR) (sizeof ARR / sizeof *ARR)
// Generate random number in the interval [M,N]
#define RAND_RNG(M,N) (M + rand() / (RAND_MAX / (N - M + 1) + 1));
 
static void swap(unsigned *a, unsigned *b) {
    unsigned tmp = *a;
    *a = *b;
    *b = tmp;
}
 
/* sort unsigned ints */
static void rad_sort_u(unsigned *from, unsigned *to, unsigned bit)
{
	if (!bit || to < from + 1) return;
 
	unsigned *ll = from, *rr = to - 1;
	for (;;) {
		/* find left most with bit, and right most without bit, swap */
		while (ll < rr && !(*ll & bit)) ll++;
		while (ll < rr &&  (*rr & bit)) rr--;
		if (ll >= rr) break;
		swap(ll, rr);
	}
 
	if (!(bit & *ll) && ll < to) ll++;
	bit >>= 1;
 
	rad_sort_u(from, ll, bit);
	rad_sort_u(ll, to, bit);
}
 
/* sort signed ints: flip highest bit, sort as unsigned, flip back */
static void radix_sort(int *a, const size_t len)
{
	size_t i;
	unsigned *x = (unsigned*) a;
 
	for (i = 0; i < len; i++) 
            x[i] ^= INT_MIN;
 
        rad_sort_u(x, x + len, INT_MIN);
 
        for (i = 0; i < len; i++) 
            x[i] ^= INT_MIN;
}
 
int main(void)
{
 
    srand(time(NULL));
    int x[16];
 
     for (size_t i = 0; i < ARR_LEN(x); i++) 
        x[i] = RAND_RNG(-128,127)
 
    radix_sort(x, ARR_LEN(x));
 
    for (size_t i = 0; i < ARR_LEN(x); i++) 
        printf("%d%c", x[i], i + 1 < ARR_LEN(x) ? ' ' : '\n');
}

C++

#include <algorithm>
#include <iostream>
#include <iterator>
 
// Radix sort comparator for 32-bit two's complement integers
class radix_test
{
    const int bit; // bit position [0..31] to examine
public:
    radix_test(int offset) : bit(offset) {} // constructor
 
    bool operator()(int value) const // function call operator
    {
        if (bit == 31) // sign bit
            return value < 0; // negative int to left partition
        else
            return !(value & (1 << bit)); // 0 bit to left partition
    }
};
 
// Least significant digit radix sort
void lsd_radix_sort(int *first, int *last)
{
    for (int lsb = 0; lsb < 32; ++lsb) // least-significant-bit
    {
        std::stable_partition(first, last, radix_test(lsb));
    }
}
 
// Most significant digit radix sort (recursive)
void msd_radix_sort(int *first, int *last, int msb = 31)
{
    if (first != last && msb >= 0)
    {
        int *mid = std::partition(first, last, radix_test(msb));
        msb--; // decrement most-significant-bit
        msd_radix_sort(first, mid, msb); // sort left partition
        msd_radix_sort(mid, last, msb); // sort right partition
    }
}
 
// test radix_sort
int main()
{
    int data[] = { 170, 45, 75, -90, -802, 24, 2, 66 };
 
    lsd_radix_sort(data, data + 8);
    // msd_radix_sort(data, data + 8);
 
    std::copy(data, data + 8, std::ostream_iterator<int>(std::cout, " "));
 
    return 0;
}

C#

using System;
 
namespace RadixSort
{
    class Program
    {
        static void Sort(int[] old)
        {
            int i, j;
            int[] tmp = new int[old.Length];
            for (int shift = 31; shift > -1; --shift)
            {
                j = 0;
                for (i = 0; i < old.Length; ++i)
                {
                    bool move = (old[i] << shift) >= 0;
                    if (shift == 0 ? !move : move)  // shift the 0's to old's head
                        old[i-j] = old[i];
                    else                            // move the 1's to tmp
                        tmp[j++] = old[i];
                }
                Array.Copy(tmp, 0, old, old.Length-j, j);
            }
        }
        static void Main(string[] args)
        {
            int[] old = new int[] { 2, 5, 1, -3, 4 };
            Console.WriteLine(string.Join(", ", old));
            Sort(old);
            Console.WriteLine(string.Join(", ", old));
            Console.Read();
        }
    }
}

Go

package main
 
import (
    "bytes"
    "encoding/binary"
    "fmt"
)
 
// declarations for word size of data
type word int32
const wordLen = 4
const highBit = -1 << 31
 
var data = []word{170, 45, 75, -90, -802, 24, 2, 66}
 
func main() {
    buf := bytes.NewBuffer(nil)
    ds := make([][]byte, len(data))
    for i, x := range data {
        binary.Write(buf, binary.LittleEndian, x^highBit)
        b := make([]byte, wordLen)
        buf.Read(b)
        ds[i] = b
    }
    bins := make([][][]byte, 256)
    for i := 0; i < wordLen; i++ {
        for _, b := range ds {
            bins[b[i]] = append(bins[b[i]], b)
        }
        j := 0
        for k, bs := range bins {
            copy(ds[j:], bs)
            j += len(bs)
            bins[k] = bs[:0]
        }
    }
    fmt.Println("original:", data)
    var w word
    for i, b := range ds {
        buf.Write(b)
        binary.Read(buf, binary.LittleEndian, &w)
        data[i] = w^highBit
    }
    fmt.Println("sorted:  ", data)
}

Java

public static int[] sort(int[] old) {
    // Loop for every bit in the integers
    for (int shift = Integer.SIZE - 1; shift > -1; shift--) {
        // The array to put the partially sorted array into
        int[] tmp = new int[old.length];
        // The number of 0s
        int j = 0;
 
        // Move the 0s to the new array, and the 1s to the old one
        for (int i = 0; i < old.length; i++) {
            // If there is a 1 in the bit we are testing, the number will be negative
            boolean move = old[i] << shift >= 0;
 
            // If this is the last bit, negative numbers are actually lower
            if (shift == 0 ? !move : move) {
                tmp[j] = old[i];
                j++;
            } else {
                // It's a 1, so stick it in the old array for now
                old[i - j] = old[i];
            }
        }
 
        // Copy over the 1s from the old array
        for (int i = j; i < tmp.length; i++) {
            tmp[i] = old[i - j];
        }
 
        // And now the tmp array gets switched for another round of sorting
        old = tmp;
    }
 
    return old;
}

import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
 
public class RSortingRadixsort00 {
 
  public RSortingRadixsort00() {
 
    return;
  }
 
  public static int[] lsdRadixSort(int[] tlist) {
 
    List<Integer> intermediates;
    int[] limits = getLimits(tlist);
    tlist = rescale(tlist, limits[1]);
 
    for (int px = 1; px <= limits[2]; ++px) {
      @SuppressWarnings("unchecked")
      Queue<Integer> bukits[] = new Queue[10];
      for (int ix = 0; ix < tlist.length; ++ix) {
        int cval = tlist[ix];
        int digit = (int) (cval / Math.pow(10, px - 1) % 10);
        if (bukits[digit] == null) {
          bukits[digit] = new LinkedList<>();
        }
        bukits[digit].add(cval);
      }
 
      intermediates = new ArrayList<>();
      for (int bi = 0; bi < 10; ++bi) {
        if (bukits[bi] != null) {
          while (bukits[bi].size() > 0) {
            int nextd;
            nextd = bukits[bi].poll();
            intermediates.add(nextd);
          }
        }
      }
 
      for (int iw = 0; iw < intermediates.size(); ++iw) {
        tlist[iw] = intermediates.get(iw);
      }
    }
 
    tlist = rescale(tlist, -limits[1]);
 
    return tlist;
  }
 
  private static int[] rescale(int[] arry, int delta) {
 
    for (int ix = 0; ix < arry.length; ++ix) {
      arry[ix] -= delta;
    }
 
    return arry;
  }
 
  private static int[] getLimits(int[] tlist) {
 
    int[] lims = new int[3];
 
    for (int i_ = 0; i_ < tlist.length; ++i_) {
      lims[0] = Math.max(lims[0], tlist[i_]);
      lims[1] = Math.min(lims[1], tlist[i_]);
    }
    lims[2] = (int) Math.ceil(Math.log10(lims[0] - lims[1]));
 
    return lims;
  }
 
  private static void runSample(String[] args) {
 
    int[][] lists = {
      new int[] { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, -0, -1, -2, -3, -4, -5, -6, -7, -8, -9, -10, },
      new int[] { -10, -9, -8, -7, -6, -5, -4, -3, -2, -1, -0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, },
      new int[] { 2, 24, 45, 0, 66, 75, 170, -802, -90, 1066, 666, },
      new int[] { 170, 45, 75, 90, 2, 24, 802, 66, },
      new int[] { -170, -45, -75, -90, -2, -24, -802, -66, },
    };
 
    long etime;
    lsdRadixSort(Arrays.copyOf(lists[0], lists[0].length)); // do one pass to set up environment to remove it from timings
 
    for (int[] tlist : lists) {
      System.out.println(array2list(tlist));
      etime = System.nanoTime();
      tlist = lsdRadixSort(tlist);
      etime = System.nanoTime() - etime;
      System.out.println(array2list(tlist));
      System.out.printf("Elapsed time: %fs%n", ((double) etime / 1_000_000_000.0));
      System.out.println();
    }
 
    return;
  }
 
  private static List<Integer> array2list(int[] arry) {
 
    List<Integer> target = new ArrayList<>(arry.length);
 
    for (Integer iv : arry) {
      target.add(iv);
    }
 
    return target;
  }
 
  public static void main(String[] args) {
 
    runSample(args);
 
    return;
  }
}

Kotlin

// version 1.1.2
 
fun radixSort(original: IntArray): IntArray {
    var old = original // Need this to be mutable
    // Loop for every bit in the integers
    for (shift in 31 downTo 0) {
        val tmp = IntArray(old.size)  // The array to put the partially sorted array into
        var j = 0                     // The number of 0s
        // Move the 0s to the new array, and the 1s to the old one
        for (i in 0 until old.size) {
            // If there is a 1 in the bit we are testing, the number will be negative
            val move = (old[i] shl shift) >= 0
            // If this is the last bit, negative numbers are actually lower
            val toBeMoved = if (shift == 0) !move else move
            if (toBeMoved)
                tmp[j++] = old[i]
            else {
                // It's a 1, so stick it in the old array for now
                old[i - j] = old[i]
            }
        }
        // Copy over the 1s from the old array
        for (i in j until tmp.size) tmp[i] = old[i - j]
        // And now the tmp array gets switched for another round of sorting
        old = tmp
    }
    return old
}
 
fun main(args: Array<String>) {
    val arrays = arrayOf(
        intArrayOf(170, 45, 75, -90, -802, 24, 2, 66),
        intArrayOf(-4, 5, -26, 58, -990, 331, 331, 990, -1837, 2028)
    )
    for (array in arrays) println(radixSort(array).contentToString())
}

Perl

#!/usr/bin/perl
use warnings;
use strict;
 
sub radix {
    my @tab = ([@_]);
 
    my $max_length = 0;
    length > $max_length and $max_length = length for @_;
    $_ = sprintf "%0${max_length}d", $_ for @{ $tab[0] }; # Add zeros.
 
    for my $pos (reverse -$max_length .. -1) {
        my @newtab;
        for my $bucket (@tab) {
            for my $n (@$bucket) {
                my $char = substr $n, $pos, 1;
                $char = -1 if '-' eq $char;
                $char++;
                push @{ $newtab[$char] }, $n;
            }
        }
        @tab = @newtab;
    }
 
    my @return;
    my $negative = shift @tab;                            # Negative bucket must be reversed.
    push @return, reverse @$negative;
    for my $bucket (@tab) {
        push @return, @{ $bucket // [] };
    }
    $_ = 0 + $_ for @return;                              # Remove zeros.
    return @return;
}

Perl 6

sub radsort (@ints) {
    my $maxlen = max @ints».chars;
    my @list = @ints».fmt("\%0{$maxlen}d");
 
    for reverse ^$maxlen -> $r {
        my @buckets = @list.classify( *.substr($r,1) ).sort: *.key;
        @buckets[0].value = @buckets[0].value.reverse.List
            if !$r and @buckets[0].key eq '-';
        @list = flat map *.value.values, @buckets;
    }
    @list».Int;
}
 
.say for radsort (-2_000 .. 2_000).roll(20);

Python

#python2.6 <
from math import log
 
def getDigit(num, base, digit_num):
    # pulls the selected digit
    return (num // base ** digit_num) % base  
 
def makeBlanks(size):
    # create a list of empty lists to hold the split by digit
    return [ [] for i in range(size) ]  
 
def split(a_list, base, digit_num):
    buckets = makeBlanks(base)
    for num in a_list:
        # append the number to the list selected by the digit
        buckets[getDigit(num, base, digit_num)].append(num)  
    return buckets
 
# concatenate the lists back in order for the next step
def merge(a_list):
    new_list = []
    for sublist in a_list:
       new_list.extend(sublist)
    return new_list
 
def maxAbs(a_list):
    # largest abs value element of a list
    return max(abs(num) for num in a_list)
 
def split_by_sign(a_list):
    # splits values by sign - negative values go to the first bucket,
    # non-negative ones into the second
    buckets = [[], []]
    for num in a_list:
        if num < 0:
            buckets[0].append(num)
        else:
            buckets[1].append(num)
    return buckets
 
def radixSort(a_list, base):
    # there are as many passes as there are digits in the longest number
    passes = int(round(log(maxAbs(a_list), base)) + 1) 
    new_list = list(a_list)
    for digit_num in range(passes):
        new_list = merge(split(new_list, base, digit_num))
    return merge(split_by_sign(new_list))

#python3.7 <
def flatten(some_list):
    """
    Flatten a list of lists.
    Usage: flatten([[list a], [list b], ...])
    Output: [elements of list a, elements of list b]
    """
    new_list = []
    for sub_list in some_list:
        new_list += sub_list
    return new_list
 
def radix(some_list, idex=None, size=None):
    """
    Recursive radix sort
    Usage: radix([unsorted list])
    Output: [sorted list]
    """
    # Initialize variables not set in the initial call
    if size == None:
        largest_num = max(some_list)
        largest_num_str = str(largest_num)
        largest_num_len = len(largest_num_str)
        size = largest_num_len
 
    if idex == None:
        idex = size
 
    # Translate the index we're looking at into an array index.
    # e.g., looking at the 10's place for 100:
    # size: 3
    # idex: 2
    #    i: (3-2) == 1
    # str(123)[i] -> 2
    i = size - idex 
 
    # The recursive base case.
    # Hint: out of range indexing errors
    if i >= size:
        return some_list
 
    # Initialize the bins we will place numbers into
    bins = [[] for _ in range(10)]
 
    # Iterate over the list of numbers we are given
    for e in some_list:
        # The destination bin; e.g.,:
        #   size: 5
        #      e: 29
        #  num_s: '00029'
        #      i: 3
        # dest_c: '2'
        # dest_i: 2
        num_s  = str(e).zfill(size)
        dest_c = num_s[i]
        dest_i = int(dest_c) 
        bins[dest_i] += [e]
 
    result = []
    for b in bins:
        # Make the recursive call
        # Sort each of the sub-lists in our bins
        result.append(radix(b, idex-1, size))
 
    # Flatten our list
    # This is also called in our recursive call,
    # so we don't need flatten to be recursive.
    flattened_result = flatten(result)
 
    return flattened_result

Ruby

class Array
  def radix_sort(base=10)
    ary = dup
    rounds = (Math.log(ary.minmax.map(&:abs).max)/Math.log(base)).floor + 1
    rounds.times do |i|
      buckets = Array.new(2*base){[]}
      base_i = base**i
      ary.each do |n|
        digit = (n/base_i) % base
        digit += base if 0<=n
        buckets[digit] << n
      end
      ary = buckets.flatten
      p [i, ary] if $DEBUG
    end
    ary
  end
  def radix_sort!(base=10)
    replace radix_sort(base)
  end
end
 
p [1, 3, 8, 9, 0, 0, 8, 7, 1, 6].radix_sort
p [170, 45, 75, 90, 2, 24, 802, 66].radix_sort
p [170, 45, 75, 90, 2, 24, -802, -66].radix_sort
p [100000, -10000, 400, 23, 10000].radix_sort

更多代码，敬请期待！
整理自网络。