C++ 计数排序实例详解

#include <iostream> 
#include <Windows.h> 
#include <assert.h> 
 
using namespace std; 
 
//计数排序，适用于无符号整形 
void CountSort(int* a, size_t size) 
{ 
  assert(a); 
  size_t max = a[0]; 
  size_t min = a[0]; 
  for (size_t i = 0; i < size; ++i) 
  { 
    if (a[i] > max) 
    { 
      max = a[i]; 
    } 
    if (a[i] < min) 
    { 
      min = a[i]; 
    } 
  } 
  size_t range = max - min + 1;   //要开辟的数组范围 
  size_t* count = new size_t[range]; 
  memset(count, 0, sizeof(size_t)*range);  //初始化为0 
  //统计每个数出现的次数 
  for (size_t i = 0; i < size; ++i)   //从原数组中取数，原数组个数为size 
  { 
    count[a[i]-min]++; 
  } 
  //写回到原数组 
  size_t index = 0; 
  for (size_t i = 0; i < range; ++i)  //从开辟的数组中读取，开辟的数组大小为range 
  { 
    while (count[i]--) 
    { 
      a[index++] = i + min; 
    } 
  } 
  delete[] count; 
} 
 
void Print(int* a, size_t size) 
{ 
  for (size_t i = 0; i < size; ++i) 
  { 
    cout << a[i] << " "; 
  } 
  cout << endl; 
} 

#include "CountSort.h" 
 
void TestCountSort() 
{ 
  int arr[] = { 1, 2, 3, 4, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 2, 2, 2, 4, 5, 8, 9, 5, 11, 11, 22, 12, 12 }; 
  size_t size = sizeof(arr) / sizeof(arr[0]); 
  CountSort(arr, size); 
  Print(arr, size); 
} 
 
int main() 
{ 
  TestCountSort(); 
  system("pause"); 
  return 0; 
}