代码

void countingSort(unsigned *input, unsigned *output, int n, int bytePos) {
    unsigned count[256] = {0};
    // Count frequency of each byte value
    for (int i = 0; i < n; i++) {
        unsigned char byte = (input[i] >> (bytePos * 8)) & 0xFF;
        count[byte]++;
    }

    // Compute cumulative sum
    for (int i = 1; i < 256; i++) {
        count[i] += count[i - 1];
    }

    // Place elements into output array in sorted order
    for (int i = n - 1; i >= 0; i--) {
        unsigned char byte = (input[i] >> (bytePos * 8)) & 0xFF;
        output[count[byte] - 1] = input[i];
        count[byte]--;
    }
}

评测结果