用c

好的，这是使用C++实现的代码：

#include <iostream>
#include <vector>
using namespace std;

void merge(vector<string>& arr, int left, int mid, int right) {
    int n1 = mid - left + 1;
    int n2 = right - mid;
    vector<string> L(n1), R(n2);
    for (int i = 0; i < n1; i++) {
        L[i] = arr[left + i];
    }
    for (int j = 0; j < n2; j++) {
        R[j] = arr[mid + 1 + j];
    }
    int i = 0, j = 0, k = left;
    while (i < n1 && j < n2) {
        if (L[i] > R[j]) {
            arr[k] = L[i];
            i++;
        }
        else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }
    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }
    while (j < n2) {
        arr[k] = R[j];
        j++;
        k++;
    }
}

void merge_sort(vector<string>& arr, int left, int right) {
    if (left < right) {
        int mid = left + (right - left) / 2;
        merge_sort(arr, left, mid);
        merge_sort(arr, mid + 1, right);
        merge(arr, left, mid, right);
    }
}

void merge_sort_desc(vector<string>& arr) {
    merge_sort(arr, 0, arr.size() - 1);
    reverse(arr.begin(), arr.end());
}

int main() {
    cout << "请输入一组字符串，以空格分隔：" << endl;
    string input;
    getline(cin, input);
    vector<string> arr;
    string temp = "";
    for (int i = 0; i < input.length(); i++) {
        if (input[i] == ' ') {
            arr.push_back(temp);
            temp = "";
        }
        else {
            temp += input[i];
        }
    }
    arr.push_back(temp);
    merge_sort_desc(arr);
    cout << "按字典顺序进行降序排序后的结果为：" << endl;
    for (auto s : arr) {
        cout << s << " ";
    }
    return 0;
}

你可以按照程序提示输入一组字符串，程序将按照字典顺序进行降序排序，并输出结果。程序中使用的是归并排序算法，时间复杂度为 O(nlogn)。