//LSD Radix Sort
var counter = [];
function radixSort(arr, maxDigit) {
    var mod = 10;
    var dev = 1;
    for (var i = 0; i < maxDigit; i++, dev *= 10, mod *= 10) {
        for(var j = 0; j < arr.length; j++) {
            var bucket = parseInt((arr[j] % mod) / dev);
            if(counter[bucket]==null) {
                counter[bucket] = [];
            }
            counter[bucket].push(arr[j]);
        }
        var pos = 0;
        for(var j = 0; j < counter.length; j++) {
            var value = null;
            if(counter[j]!=null) {
                while ((value = counter[j].shift()) != null) {
                      arr[pos++] = value;
                }
          }
        }
    }
    return arr;
}

/**
 * 基数排序
 * 考虑负数的情况还可以参考： https://code.i-harness.com/zh-CN/q/e98fa9
 */
public class RadixSort implements IArraySort {

    @Override
    public int[] sort(int[] sourceArray) throws Exception {
        // 对 arr 进行拷贝，不改变参数内容
        int[] arr = Arrays.copyOf(sourceArray, sourceArray.length);

        int maxDigit = getMaxDigit(arr);
        return radixSort(arr, maxDigit);
    }

    /**
     * 获取最高位数
     */
    private int getMaxDigit(int[] arr) {
        int maxValue = getMaxValue(arr);
        return getNumLenght(maxValue);
    }

    private int getMaxValue(int[] arr) {
        int maxValue = arr[0];
        for (int value : arr) {
            if (maxValue < value) {
                maxValue = value;
            }
        }
        return maxValue;
    }

    protected int getNumLenght(long num) {
        if (num == 0) {
            return 1;
        }
        int lenght = 0;
        for (long temp = num; temp != 0; temp /= 10) {
            lenght++;
        }
        return lenght;
    }

    private int[] radixSort(int[] arr, int maxDigit) {
        int mod = 10;
        int dev = 1;

        for (int i = 0; i < maxDigit; i++, dev *= 10, mod *= 10) {
            // 考虑负数的情况，这里扩展一倍队列数，其中 [0-9]对应负数，[10-19]对应正数 (bucket + 10)
            int[][] counter = new int[mod * 2][0];

            for (int j = 0; j < arr.length; j++) {
                int bucket = ((arr[j] % mod) / dev) + mod;
                counter[bucket] = arrayAppend(counter[bucket], arr[j]);
            }

            int pos = 0;
            for (int[] bucket : counter) {
                for (int value : bucket) {
                    arr[pos++] = value;
                }
            }
        }

        return arr;
    }

    /**
     * 自动扩容，并保存数据
     *
     * @param arr
     * @param value
     */
    private int[] arrayAppend(int[] arr, int value) {
        arr = Arrays.copyOf(arr, arr.length + 1);
        arr[arr.length - 1] = value;
        return arr;
    }
}

function radixSort($arr, $maxDigit = null)
{
    if ($maxDigit === null) {
        $maxDigit = max($arr);
    }
    $counter = [];
    for ($i = 0; $i < $maxDigit; $i++) {
        for ($j = 0; $j < count($arr); $j++) {
            preg_match_all('/\d/', (string) $arr[$j], $matches);
            $numArr = $matches[0];
            $lenTmp = count($numArr);
            $bucket = array_key_exists($lenTmp - $i - 1, $numArr)
                ? intval($numArr[$lenTmp - $i - 1])
                : 0;
            if (!array_key_exists($bucket, $counter)) {
                $counter[$bucket] = [];
            }
            $counter[$bucket][] = $arr[$j];
        }
        $pos = 0;
        for ($j = 0; $j < count($counter); $j++) {
            $value = null;
            if ($counter[$j] !== null) {
                while (($value = array_shift($counter[$j])) !== null) {
                    $arr[$pos++] = $value;
                }
          }
        }
    }

    return $arr;
}

int maxbit(int data[], int n) //辅助函数，求数据的最大位数
{
    int maxData = data[0];              ///< 最大数
    /// 先求出最大数，再求其位数，这样有原先依次每个数判断其位数，稍微优化点。
    for (int i = 1; i < n; ++i)
    {
        if (maxData < data[i])
            maxData = data[i];
    }
    int d = 1;
    int p = 10;
    while (maxData >= p)
    {
        //p *= 10; // Maybe overflow
        maxData /= 10;
        ++d;
    }
    return d;
/*    int d = 1; //保存最大的位数
    int p = 10;
    for(int i = 0; i < n; ++i)
    {
        while(data[i] >= p)
        {
            p *= 10;
            ++d;
        }
    }
    return d;*/
}
void radixsort(int data[], int n) //基数排序
{
    int d = maxbit(data, n);
    int *tmp = new int[n];
    int *count = new int[10]; //计数器
    int i, j, k;
    int radix = 1;
    for(i = 1; i <= d; i++) //进行d次排序
    {
        for(j = 0; j < 10; j++)
            count[j] = 0; //每次分配前清空计数器
        for(j = 0; j < n; j++)
        {
            k = (data[j] / radix) % 10; //统计每个桶中的记录数
            count[k]++;
        }
        for(j = 1; j < 10; j++)
            count[j] = count[j - 1] + count[j]; //将tmp中的位置依次分配给每个桶
        for(j = n - 1; j >= 0; j--) //将所有桶中记录依次收集到tmp中
        {
            k = (data[j] / radix) % 10;
            tmp[count[k] - 1] = data[j];
            count[k]--;
        }
        for(j = 0; j < n; j++) //将临时数组的内容复制到data中
            data[j] = tmp[j];
        radix = radix * 10;
    }
    delete []tmp;
    delete []count;
}

#include<stdio.h>
#define MAX 20
//#define SHOWPASS
#define BASE 10

void print(int *a, int n) {
  int i;
  for (i = 0; i < n; i++) {
    printf("%d\t", a[i]);
  }
}

void radixsort(int *a, int n) {
  int i, b[MAX], m = a[0], exp = 1;

  for (i = 1; i < n; i++) {
    if (a[i] > m) {
      m = a[i];
    }
  }

  while (m / exp > 0) {
    int bucket[BASE] = { 0 };

    for (i = 0; i < n; i++) {
      bucket[(a[i] / exp) % BASE]++;
    }

    for (i = 1; i < BASE; i++) {
      bucket[i] += bucket[i - 1];
    }

    for (i = n - 1; i >= 0; i--) {
      b[--bucket[(a[i] / exp) % BASE]] = a[i];
    }

    for (i = 0; i < n; i++) {
      a[i] = b[i];
    }

    exp *= BASE;

#ifdef SHOWPASS
    printf("\nPASS   : ");
    print(a, n);
#endif
  }
}

int main() {
  int arr[MAX];
  int i, n;

  printf("Enter total elements (n <= %d) : ", MAX);
  scanf("%d", &n);
  n = n < MAX ? n : MAX;

  printf("Enter %d Elements : ", n);
  for (i = 0; i < n; i++) {
    scanf("%d", &arr[i]);
  }

  printf("\nARRAY  : ");
  print(&arr[0], n);

  radixsort(&arr[0], n);

  printf("\nSORTED : ");
  print(&arr[0], n);
  printf("\n");

  return 0;
}

-- 获取表中位数
local maxBit = function (tt)
    local weight = 10;      -- 十進制
    local bit = 1;
   
    for k, v in pairs(tt) do
        while v >= weight do
            weight = weight * 10;
            bit = bit + 1;  
        end
    end
    return bit;
end
-- 基数排序
local radixSort = function (tt)
    local maxbit = maxBit(tt);

    local bucket = {};
    local temp = {};
    local radix = 1;
    for i = 1, maxbit do
        for j = 1, 10 do
            bucket[j] = 0;      --- 清空桶
        end
        for k, v in pairs(tt) do
            local remainder = math.floor((v / radix)) % 10 + 1;    
            bucket[remainder] = bucket[remainder] + 1;      -- 每個桶數量自動增加1
        end
       
        for j = 2, 10 do
            bucket[j] = bucket[j - 1] + bucket[j];  -- 每个桶的数量 = 以前桶数量和 + 自个数量
        end
        -- 按照桶的位置，排序--这个是桶式排序，必须使用倒序，因为排序方法是从小到大，顺序下来，会出现大的在小的上面清空。
        for k = #tt, 1, -1 do
            local remainder = math.floor((tt[k] / radix)) % 10 + 1;
            temp[bucket[remainder]] = tt[k];
            bucket[remainder] = bucket[remainder] - 1;
        end
        for k, v in pairs(temp) do
            tt[k] = v;
        end
        radix = radix * 10;
    end
end;