C++从基础语法到递归、重载与宏定义

#include <iostream>
#include <cmath>
// 判定素数函数
bool isPrime(int n) {
    if (n < 2) return false;
    for (int i = 2; i <= sqrt(n); ++i) {
        if (n % i == 0) return false;
    }
    return true;
}
int main()
{
    int num;
    std::cout << "输入一个整数: ";
    std::cin >> num;
    if (isPrime(num)) std::cout << num << " 是素数" << std::endl;
    else std::cout << num << " 不是素数" << std::endl;
    return 0;
}

#include <iostream>
// 统计函数：通过引用返回结果
void countNumber(int &odd, int &even) {
    int val;
    while (std::cin >> val && val != 0) {
        if (val % 2 == 0) even++;
        else odd++;
    }
}
int main() 
{
    int oddCount = 0, evenCount = 0;
    std::cout << "请输入一列整数（0结束）: " << std::endl;
    countNumber(oddCount, evenCount);
    std::cout << "奇数: " << oddCount << " 个，偶数: " << evenCount << " 个" << std::endl;
    return 0;
}

#include <iostream>
long long factorial(int n = 5) {
    long long res = 1;
    for (int i = 1; i <= n; ++i) res *= i;
    return res;
}
int main() 
{
    // 给出实参
    std::cout << "3! = " << factorial(3) << std::endl;
    // 不给实参，使用默认值 5
    std::cout << "默认(5!) = " << factorial() << std::endl;
    return 0;
}

#include <iostream>
long long fac(int n) {
    long long res = 1;
    for (int i = 1; i <= n; ++i) res *= i;
    return res;
}
long long add(long long x, long long y, long long z) {
    return x + y + z;
}
int main() 
{
    int a, b, c;
    std::cout << "输入 a, b, c: ";
    std::cin >> a >> b >> c;
    std::cout << "结果: " << add(fac(a), fac(b), fac(c)) << std::endl;
    return 0;
}

#include <iostream>
bool isLeapYear(int year) {
    return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
}
int main() 
{
    int y;
    std::cout << "输入年份: ";
    std::cin >> y;
    if (isLeapYear(y)) std::cout << "是闰年" << std::endl;
    else std::cout << "不是闰年" << std::endl;
    return 0;
}

#include <iostream>
int fib(int n) {
    if (n == 1 || n == 2) return 1;
    return fib(n - 1) + fib(n - 2);
}
int main() 
{
    int n;
    std::cout << "输入 n: ";
    std::cin >> n;
    std::cout << "第 " << n << " 个数是: " << fib(n) << std::endl;
    return 0;
}

#include <iostream>
#include <cmath>
bool prime(int n) {
    if (n < 2) return false;
    for (int i = 2; i <= sqrt(n); i++) {
        if (n % i == 0) return false;
    }
    return true;
}
void gotbaha(int n) {
    for (int i = 2; i <= n / 2; i++) {
        if (prime(i) && prime(n - i)) {
            std::cout << n << "=" << i << "+" << (n - i) << std::endl;
            return;
        }
    }
}
int main() 
{
    int n;
    std::cout << "输入一个偶数: ";
    std::cin >> n;
    if (n >= 6 && n % 2 == 0) gotbaha(n);
    else std::cout << "程序结束" << std::endl;
    return 0;
}

#include <iostream>
int add(int a, int b, int c) { return a + b + c; }
float add(float a, float b) { return a + b; }
int main() 
{
    std::cout << "3个整数和: " << add(1, 2, 3) << std::endl;
    std::cout << "2个浮点数和: " << add(1.5f, 2.5f) << std::endl;
    return 0;
}

#include <iostream>
inline int getSum(int m, int n) { return m + n; }
int main() 
{
    int m, n;
    std::cin >> m >> n;
    std::cout << "和为: " << getSum(m, n) << std::endl;
    return 0;
}

#ifndef MY_MAX_H
#define MY_MAX_H
inline double getMax(double a, double b) { return (a > b) ? a : b; }
#endif

#include <iostream>
#include "my_max.h"
int main() 
{
    double a, b, c;
    std::cin >> a >> b >> c;
    double res = getMax(getMax(a, b), c);
    std::cout << "最大值: " << res << std::endl;
    return 0;
}

#include <iostream>
#define MUL(a, b) ((a) * (b))
int main() 
{
    int x, y;
    std::cin >> x >> y;
    std::cout << "乘积: " << MUL(x, y) << std::endl;
    return 0;
}

#include <iostream>
void reverse(int n) {
    if (n == 0) return;
    std::cout << n % 10;
    reverse(n / 10);
}
int main() 
{
    int n;
    std::cout << "输入整数: ";
    std::cin >> n;
    if (n == 0) std::cout << "0";
    else reverse(n);
    std::cout << std::endl;
    return 0;
}