8.基数排序

#include <iostream>
#include <cmath>
#include <cstring>
using namespace std; 

int bits(int t)
{
    int ret = 0;
    while(t >= 10)
    { ret++; t /= 10; }
    return ret + 1;
}

int find_p(int n, int j)
{
    return (n / (int)pow(10, j - 1)) - (n / (int)pow(10, j)) * 10;
}

bool Radix_sort(int *a, int n, int k)
{
    int bit = bits(k), *b = new int [n];
    int counter[10];
    
    for(int j = 1; j <= bit; j++)
    {    
        memset(counter, 0, sizeof(counter));
        
        for(int i = 0; i < n; i++)
            counter[find_p(a[i], j)]++;
    
        for(int i = 1; i < 10; i++)
            counter[i] += counter[i - 1];
            
        for(int i = n - 1; i >= 0; i--)
            b[counter[find_p(a[i], j)]-- - 1] = a[i];    
        
        for(int i = 0; i < n; i++)
            a[i] = b[i];
    }
    return true;
}

int main()
{    
    int n;
    cin >> n;
    int *num = new int[n];
    int *k = &num[0];
    for(int i = 0; i < n; i++)
    {
        cin >> num[i];
        if(*k <= num[i]) k = &num[i];
    }
    
    Radix_sort(num, n, *k);
    
    for(int i = 0; i < n; i++)
        cout << num[i] << " ";
    cout << endl;
}