计数排序与基数排序

#include<iostream>
#include<stdlib.h>
#include<cstring> 
using namespace std;

int main()
{
    int n;
    cin >> n;
    int *a = new int[n];
    int *c = new int[n];
    memset(a, 0, n*sizeof(int));
    memset(c, 0, (n+1)*sizeof(int));
    int max = 0;
    
    for (int i = 0; i < n; i++)
    {
        cin >> a[i];//a记录元素 
        max = a[i]>max ? a[i] : max;
    }
    int *b = new int[max+1];
    memset(b, 0, (max+1)*sizeof(int));
    for (int i = 0; i < n; i++)
    {
        b[a[i]]++;//代表当前数字的排名 
    }
    for (int i = 1; i < max + 1; i++)
    {
        b[i] = b[i] + b[i - 1];
    }
    for (int i = 0; i < n; i++)
    {
        b[a[i]]--;
        c[b[a[i]]] = a[i];
    }
    for (int i = 0; i < n; i++)
        cout << c[i] << endl;
    delete[]a;
    delete[]b;
    delete[]c;

    return 0;
}

int getDigit(int i, int d)    //d的值为1、2、3...，表示要求取的相应位的值，1表示求取个位，
{                              //2表示十分位，类推
    int val;
    while (d--)
    {
        val = i % 10;
        i /= 10;
    }
    return val;
}

//基数排序算法的具体实现
void RadixSort(int *list, int begin, int end, int digit)
{
    int radix = 10; //基数 进制 
    int i = 0, j = 0;
    int * count = new int[radix];   //存放各个桶的数据存放个数
    int * bucket = new int[end - begin + 1];

    for (int d = 1; d <= digit; d++)
    {
        for ( i = 0; i < radix; i++)
            count[i] = 0;        //置空各个桶的统计数据

        for (i = begin; i <= end; i++)
        {
            j = getDigit(list[i], d);
            count[j]++;
        }

        for (i = 1; i < radix; i++)
            count[i] = count[i] + count[i - 1]; //count[i]表示第i个桶的右边界索引

        //将数据依次装入桶中，保证数据的稳定性，此步即为基数排序的分配
        for (i = end; i >= begin; i--)
        {
            j = getDigit(list[i], d);
            bucket[count[j] - 1] = list[i];
            count[j]--;
        }

        //基数排序的收集
        //把桶中的数据再倒出来
        for (i = begin, j = 0; i <= end; i++, j++)
            list[i] = bucket[j];
    }
}