Question

如何使用Radix Sort对数组中的某些浮点数据进行排序？我认为我应该将所有数据乘以10的最小幂，这使得它们成为整数。但我不知道我怎么能理解那种合适的力量。这是用于排序整数数组的c ++代码。有人可以帮我这么做吗？

#include<iostream>
using namespace std;
//Get maximum value in arr[]

    int findMax(int arr[], int n)
{
    int max = arr[0];
     for (int i = 1; i < n; i++)
      if (arr[i] > max)
        max = arr[i];
    return max;
}

// A function to do counting sort of arr[] according to
// the digit represented by exp.

    void countSort(int arr[], int n, int exp)
{
    int outputArr[n]; // output array
    int i, count[10] = {0};

// Store count of occurrences in count[]

    for (i = 0; i < n; i++)
      count[ (arr[i]/exp)%10 ]++;

// Change count[i] so that count[i] now contains actual
//  position of this digit in output[]

    for (i = 1; i < 10; i++)
      count[i] += count[i - 1];

// Build the output array

    for (i = n - 1; i >= 0; i--)
   {
      outputArr[count[ (arr[i]/exp)%10 ] - 1] = arr[i];
      count[ (arr[i]/exp)%10 ]--;
   }

// Copy the output array to arr[], so that arr[] now
// contains sorted numbers according to current digit

    for (i = 0; i < n; i++)
      arr[i] = outputArr[i];
}

// The main function to that sorts arr[] of size n using Radix Sort

    void radixsort(int arr[], int n)
    {

      int max = findMax(arr, n);

// Do counting sort for every digit. Note that instead
// of passing digit number, exp is passed. exp is 10^i
// where i is current digit number

  for (int exp = 1; max/exp > 0; exp *= 10)
    countSort(arr, n, exp);
    }

// A utility function to print an array

    void print(int arr[], int n)
    {
       for (int i = 0; i < n; i++)
        cout << arr[i] << " ";
    }

   int main()
 {
    int arr[] = {506,2,41,33,5,965,73};
    int n = sizeof(arr)/sizeof(arr[0]);
    radixsort(arr, n);
    print(arr, n);
    return 0;
 }

Answer 1

除了像NAN这样的特殊数字，您可以将浮点数视为32位符号+幅度数，以便进行排序。对于基数排序，将符号+幅度数转换为32位无符号整数最简单，然后在排序后转换回来。示例宏从float转换为unsigned，从unsigned转换为float。请注意，-0将被视为小于+0，但这不应该是一个问题。在使用这些宏之前，将float转换为unsigned int。

#define FLOAT_2_U(x) ((x)^(((~(x) >> 31)-1) | 0x80000000))
#define U_2_FLOAT(x) ((x)^((( (x) >> 31)-1) | 0x80000000))

如何使用Radix Sort作为浮点数的数组？

1 个答案: