用c++做一个小小计算器，它能够实现以下功能 1 加法 2 减法 3 乘法 4 除法 5 取模运算 6 判断数字的位数 7 计算圆面积 8 判断闰年 9 成绩转换 10 计算从1到输入数之间的奇数和 11 计算从1到输入数之间的偶数和 12 输出从1到输入数之间所有3的倍数 13 求即被3整除又被5整除的数 14 求水仙花数 15 求最大值 16 求最大最小值 17 数组—冒泡排序 18 数组-矩阵转置 19 数组-求矩阵对角线和 20 统计单词输入个数 21 静态创建链表 22 动态创建链表 23 学生成绩排序 24 学生成绩普涨10分 25 退出

好的，以下是一个简单的实现：

#include <iostream>
#include <cmath>

using namespace std;

int main() {
    int choice = 0;
    while (choice != 25) {
        cout << "请选择要进行的操作：" << endl;
        cout << "1. 加法" << endl;
        cout << "2. 减法" << endl;
        cout << "3. 乘法" << endl;
        cout << "4. 除法" << endl;
        cout << "5. 取模运算" << endl;
        cout << "6. 判断数字的位数" << endl;
        cout << "7. 计算圆面积" << endl;
        cout << "8. 判断闰年" << endl;
        cout << "9. 成绩转换" << endl;
        cout << "10. 计算从1到输入数之间的奇数和" << endl;
        cout << "11. 计算从1到输入数之间的偶数和" << endl;
        cout << "12. 输出从1到输入数之间所有3的倍数" << endl;
        cout << "13. 求即被3整除又被5整除的数" << endl;
        cout << "14. 求水仙花数" << endl;
        cout << "15. 求最大值" << endl;
        cout << "16. 求最大最小值" << endl;
        cout << "17. 数组—冒泡排序" << endl;
        cout << "18. 数组-矩阵转置" << endl;
        cout << "19. 数组-求矩阵对角线和" << endl;
        cout << "20. 统计单词输入个数" << endl;
        cout << "21. 静态创建链表" << endl;
        cout << "22. 动态创建链表" << endl;
        cout << "23. 学生成绩排序" << endl;
        cout << "24. 学生成绩普涨10分" << endl;
        cout << "25. 退出" << endl;
        cin >> choice;
        switch (choice) {
            case 1: {
                double a, b;
                cout << "请输入两个数：";
                cin >> a >> b;
                cout << "它们的和为：" << a + b << endl;
                break;
            }
            case 2: {
                double a, b;
                cout << "请输入两个数：";
                cin >> a >> b;
                cout << "它们的差为：" << a - b << endl;
                break;
            }
            case 3: {
                double a, b;
                cout << "请输入两个数：";
                cin >> a >> b;
                cout << "它们的积为：" << a * b << endl;
                break;
            }
            case 4: {
                double a, b;
                cout << "请输入两个数：";
                cin >> a >> b;
                if (b == 0) {
                    cout << "除数不能为0！" << endl;
                } else {
                    cout << "它们的商为：" << a / b << endl;
                }
                break;
            }
            case 5: {
                int a, b;
                cout << "请输入两个整数：";
                cin >> a >> b;
                cout << "它们的模为：" << a % b << endl;
                break;
            }
            case 6: {
                int n;
                cout << "请输入一个整数：";
                cin >> n;
                int digits = 1;
                while (n >= 10) {
                    n /= 10;
                    digits++;
                }
                cout << "它的位数为：" << digits << endl;
                break;
            }
            case 7: {
                double r;
                cout << "请输入圆的半径：";
                cin >> r;
                double area = M_PI * r * r;
                cout << "它的面积为：" << area << endl;
                break;
            }
            case 8: {
                int year;
                cout << "请输入一个年份：";
                cin >> year;
                if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
                    cout << year << "年是闰年" << endl;
                } else {
                    cout << year << "年不是闰年" << endl;
                }
                break;
            }
            case 9: {
                double score;
                cout << "请输入成绩：";
                cin >> score;
                if (score >= 90) {
                    cout << "等级为：A" << endl;
                } else if (score >= 80) {
                    cout << "等级为：B" << endl;
                } else if (score >= 70) {
                    cout << "等级为：C" << endl;
                } else if (score >= 60) {
                    cout << "等级为：D" << endl;
                } else {
                    cout << "等级为：E" << endl;
                }
                break;
            }
            case 10: {
                int n, sum = 0;
                cout << "请输入一个整数：";
                cin >> n;
                for (int i = 1; i <= n; i += 2) {
                    sum += i;
                }
                cout << "从1到" << n << "之间的奇数和为：" << sum << endl;
                break;
            }
            case 11: {
                int n, sum = 0;
                cout << "请输入一个整数：";
                cin >> n;
                for (int i = 2; i <= n; i += 2) {
                    sum += i;
                }
                cout << "从1到" << n << "之间的偶数和为：" << sum << endl;
                break;
            }
            case 12: {
                int n;
                cout << "请输入一个整数：";
                cin >> n;
                cout << "从1到" << n << "之间所有3的倍数为：";
                for (int i = 3; i <= n; i += 3) {
                    cout << i << " ";
                }
                cout << endl;
                break;
            }
            case 13: {
                int n;
                cout << "请输入一个整数：";
                cin >> n;
                cout << "即被3整除又被5整除的数有：";
                for (int i = 1; i <= n; i++) {
                    if (i % 3 == 0 && i % 5 == 0) {
                        cout << i << " ";
                    }
                }
                cout << endl;
                break;
            }
            case 14: {
                int n;
                cout << "请输入一个整数：";
                cin >> n;
                cout << "水仙花数有：";
                for (int i = 100; i <= n; i++) {
                    int a = i / 100;
                    int b = i / 10 % 10;
                    int c = i % 10;
                    if (i == a * a * a + b * b * b + c * c * c) {
                        cout << i << " ";
                    }
                }
                cout << endl;
                break;
            }
            case 15: {
                double a, b;
                cout << "请输入两个数：";
                cin >> a >> b;
                double maxNum = a > b ? a : b;
                cout << "它们的最大值为：" << maxNum << endl;
                break;
            }
            case 16: {
                double a, b;
                cout << "请输入两个数：";
                cin >> a >> b;
                double maxNum = a > b ? a : b;
                double minNum = a < b ? a : b;
                cout << "它们的最大值为：" << maxNum << endl;
                cout << "它们的最小值为：" << minNum << endl;
                break;
            }
            case 17: {
                int n;
                cout << "请输入数组元素个数：";
                cin >> n;
                int a[n];
                cout << "请输入数组元素：";
                for (int i = 0; i < n; i++) {
                    cin >> a[i];
                }
                for (int i = 0; i < n - 1; i++) {
                    for (int j = 0; j < n - i - 1; j++) {
                        if (a[j] > a[j + 1]) {
                            int temp = a[j];
                            a[j] = a[j + 1];
                            a[j + 1] = temp;
                        }
                    }
                }
                cout << "排序后的数组为：";
                for (int i = 0; i < n; i++) {
                    cout << a[i] << " ";
                }
                cout << endl;
                break;
            }
            case 18: {
                int m, n;
                cout << "请输入矩阵的行数和列数：";
                cin >> m >> n;
                int a[m][n];
                cout << "请输入矩阵元素：";
                for (int i = 0; i < m; i++) {
                    for (int j = 0; j < n; j++) {
                        cin >> a[i][j];
                    }
                }
                cout << "转置后的矩阵为：" << endl;
                for (int i = 0; i < n; i++) {
                    for (int j = 0; j < m; j++) {
                        cout << a[j][i] << " ";
                    }
                    cout << endl;
                }
                break;
            }
            case 19: {
                int n;
                cout << "请输入矩阵的行数和列数：";
                cin >> n;
                int a[n][n];
                cout << "请输入矩阵元素：";
                for (int i = 0; i < n; i++) {
                    for (int j = 0; j < n; j++) {
                        cin >> a[i][j];
                    }
                }
                int sum = 0;
                for (int i = 0; i < n; i++) {
                    sum += a[i][i];
                }
                cout << "矩阵对角线元素之和为：" << sum << endl;
                break;
            }
            case 20: {
                string s;
                cout << "请输入一个字符串：";
                cin >> s;
                int count = 1;
                for (int i = 0; i < s.length(); i++) {
                    if (s[i] == ' ') {
                        count++;
                    }
                }
                cout << "单词个数为：" << count << endl;
                break;
            }
            case 21: {
                struct ListNode {
                    int val;
                    ListNode *next;
                    ListNode(int x) : val(x), next(NULL) {}
                };
                ListNode *head = new ListNode(0);
                ListNode *p = head;
                int n;
                cout << "请输入链表元素个数：";
                cin >> n;
                cout << "请输入链表元素：";
                for (int i = 0; i < n; i++) {
                    int x;
                    cin >> x;
                    ListNode *node = new ListNode(x);
                    p->next = node;
                    p = p->next;
                }
                p = head->next;
                cout << "链表元素为：";
                while (p != NULL) {
                    cout << p->val << " ";
                    p = p->next;
                }
                cout << endl;
                break;
            }
            case 22: {
                struct ListNode {
                    int val;
                    ListNode *next;
                    ListNode(int x) : val(x), next(NULL) {}
                };
                ListNode *head = new ListNode(0);
                ListNode *p = head;
                int n;
                cout << "请输入链表元素个数：";
                cin >> n;
                cout << "请输入链表元素：";
                for (int i = 0; i < n; i++) {
                    int x;
                    cin >> x;
                    ListNode *node = new ListNode(x);
                    p->next = node;
                    p = p->next;
                }
                p = head->next;
                cout << "链表元素为：";
                while (p != NULL) {
                    cout << p->val << " ";
                    p = p->next;
                }
                cout << endl;
                break;
            }
            case 23: {
                struct Student {
                    string name;
                    int score;
                };
                int n;
                cout << "请输入学生人数：";
                cin >> n;
                Student students[n];
                cout << "请输入学生姓名和成绩：";
                for (int i = 0; i < n; i++) {
                    cin >> students[i].name >> students[i].score;
                }
                for (int i = 0; i < n - 1; i++) {
                    for (int j = 0; j < n - i - 1; j++) {
                        if (students[j].score < students[j + 1].score) {
                            Student temp = students[j];
                            students[j] = students[j + 1];
                            students[j + 1] = temp;
                        }
                    }
                }
                cout << "学生排名为：" << endl;
                for (int i = 0; i < n; i++) {
                    cout << i + 1 << ". " << students[i].name << " " << students[i].score << endl;
                }
                break;
            }
            case 24: {
                struct Student {
                    string name;
                    int score;
                };
                int n;
                cout << "请输入学生人数：";
                cin >> n;
                Student students[n];
                cout << "请输入学生姓名和成绩：";
                for (int i = 0; i < n; i++) {
                    cin >> students[i].name >> students[i].score;
                    students[i].score += 10;
                }
                cout << "学生成绩普涨10分后为：" << endl;
                for (int i = 0; i < n; i++) {
                    cout << students[i].name << " " << students[i].score << endl;
                }
                break;
            }
            case 25: {
                cout << "已退出" << endl;
                break;
            }
            default: {
                cout << "无效操作，请重新选择" << endl;
                break;
            }
        }
    }
    return 0;
}

这个计算器实现了所有的功能。你可以根据需要删除或添加功能。