排序算法时间效率测试

对快速排序，归并排序，希尔排序的时间效率进行了一个测试。

归并排序果然厉害，我的希尔排序写的估计有点问题，太慢。

#include 
#include 
#include 
#include 
using namespace std;
//quick sort
int partition(int *data, int first, int last) {
    int p = first;
    int pivot = data[first];
    while (first <= last) {   // 细节1  
        if (data[first] <= pivot) {
            ++first;
        }
        else if (data[last] >= pivot) {
            --last;
        }
        else {
            swap(data[first], data[last]);  // #include。细节： 不用++first， --last  
        }
    }
    swap(data[p], data[last]);
    return last;
}
void quick_sort(int *data, int first, int last, int *tmp) {
    if (first >= last) {
        return;
    }
    else {
        int index = partition(data, first, last);
        quick_sort(data, first, index - 1, tmp);
        quick_sort(data, index + 1, last, tmp);
    }
}

// bubble sort
void bubble_sort(int *data, int first, int last) {
    for (int t = 0; t < last - first; ++t) {
        for (int i = 0; i < last - t; ++i) {
            if (data[i] > data[i + 1]) {
                swap(data[i], data[i + 1]);
            }
        }
    }
}
//merge sort
void merge_data(int *data, int first, int mid, int last, int *tmp) {
    int p1 = first; int p2 = mid + 1; int index = 0;
    while (p1 <= mid && p2 <= last) {
        if (data[p1] < data[p2]) {
            tmp[index++] = data[p1++];
        }
        else {
            tmp[index++] = data[p2++];
        }
    }
    while (p1 <= mid) {
        tmp[index++] = data[p1++];
    }
    while (p2 <= last) {
        tmp[index++] = data[p2++];
    }
    // 把tmp还给data  
    for (int i = first; i <= last; ++i) {
        data[i] = tmp[i - first];
    }
}
void merge_sort(int *data, int first, int last, int *tmp) {
    if (first >= last) {
        return;
    }
    else {
        //int *tmp = new int[last - first + 1];
        int mid = first + (last - first) / 2;
        merge_sort(data, first, mid, tmp);
        merge_sort(data, mid + 1, last, tmp);
        merge_data(data, first, mid, last, tmp);
    }
}


//select sort
void select_sort(int *data, int first, int last) {
    for (int i = first; i <= last - 1; ++i) {
        int min = i;
        for (int k = i + 1; k <= last; ++k) {
            if (data[k] < data[min]) {
                min = k;
            }
        }
        swap(data[i], data[min]);
    }
}
// insert sort
void insert_sort(int *data, int first, int last) {
    for (int i = first + 1; i <= last; ++i) {
        for (int k = i; k >=  first + 1; --k) {
            if (data[k] < data[k - 1]) {
                swap(data[k], data[k - 1]);
            }
            else {
                break;
            }
        }
    }
}
// shell sort 
void shell_sort(int *data, int first, int last, int *tmp) {
    int N = last - first + 1;
    //三层循环，有点儿小复杂
    for (int gap = N / 3; gap >= 1; gap /= 2) {
        //
        for (int i = first + gap; i <= last; ++i) {
            //
            for (int k = i; k >= first + gap; k -= gap) {
                if (data[k] < data[k - gap]) {
                    swap(data[k], data[k - gap]);
                }
                else {
                    break;
                }
            }
        }
    }
}

int main() {
    int base = 2; int N = 25; int len = 0;
    void(*sort[])(int *, int, int, int *) = {
        quick_sort,
        merge_sort,
        shell_sort
        //select_sort,
        //insert_sort, 
        //bubble_sort
    };
    ofstream log("data.txt");
    for (int i = 15; i <= N; ++i) {
        log << i << endl;
        len = pow(base, i);
        int *data = new int[len];
        int *tmp = new int[len];
        for_each(data, data + len, [](int &i) -> void{ i = rand(); });

        for (int i = 0; i < sizeof(sort) / sizeof(sort[0]); ++i) {
            random_shuffle(data, data + len);

            clock_t start = clock();
            sort[i](data, 0, len - 1, tmp);
            clock_t end = clock();

            if (!is_sorted(data, data + len)) {
                log << "error\n";
            }
            else {
                log << double(end - start) / CLOCKS_PER_SEC << endl;
            }
        }
        delete[] data;
        delete[] tmp;
        log << "\n\n\n";
    }
    log.close();
    return 0;
}