代码

#include <vector>
#include <algorithm>

void sort(unsigned *a, int n) {
    std::vector<unsigned> radix(n);
    for (int i = 0; i < n; i++) {
        radix[i] = i;
    }

    std::vector<unsigned> sum(1u << 8);
    std::vector<unsigned> temp(n);
       
    for (int j = 0, k = 1u << 8; j < 4; j++, k <<= 8) {
        for (int i = 0; i < n; i++) {
            sum[(a[radix[i]] & ((k - 1) ^ ((k >> 8) - 1)))]++;
        }
        for (int i = 0; i + 1 < (1u << 8); i++) {
            sum[i + 1] += sum[i];
        }
        for (int i = 0; i < n; i++) {
            temp[sum[(a[radix[i]] & ((k - 1) ^ ((k >> 8) - 1)))]++] = radix[i];
        }
        radix.swap(temp);
        for (int i = 0; i < (1u << 8); i++) {
            sum[i] = 0;
        }
    }

    for (int i = 0; i < n; i++) {
        temp[i] = a[radix[i]];
    }
    for (int i = 0; i < n; i++) {
        a[i] = temp[i];
    }
}

评测结果