计数and基数排序

#include<iostream>
#include<algorithm>
#include<memory>//the hearder file of shared_ptr
#include <vector>
#include <list>
#include <map>
#include <string>
//#include <cstring>
#include <set>

using namespace std;

void cnt_sort(int *B, int *A, int n,int k) {//k为计数范围
    unique_ptr<int[]> C(new int[k]);

    for (int i = 0;i < k;i++)C[i] = 0;
    for (int i = 0;i < n;i++)C[A[i]]++;

    for (int i = 1;i < k;i++)C[i] += C[i - 1];

    for (int i = n - 1;i >= 0;i--)
        B[--C[A[i]]] = A[i];
        
}

void radix_sort(int *A, int n) {//n为待排序数组大小

    int maxval = 0;//假设数组全为正数
    for (int i = 0;i < n;i++)if (maxval < A[i])maxval = A[i];
    int position = 1;
    int *tmp = new int[n];

    while (maxval) {
        vector<int> count(n, 0);
        for (int i = 0;i < n;i++)count[A[i] / position % 10]++;
        for (int i = 1;i < n;i++)count[i] += count[i - 1];

        for (int i = n;i > 0;i--)tmp[--count[A[i - 1] / position % 10]] = A[i - 1];//反向遍历保证排序的稳定
        memcpy(A, tmp, sizeof(int)*n);
        
        position *= 10;
        maxval /= 10;
    }
}