使用引用交换两个变量

#include <iostream>

using namespace std;

void swap2(int &a, int &b) {
    int t = a;
    a = b;
    b = t;
}

int main() {
    int a = 3, b = 4;
    swap2(a, b);
    cout << a << " " << b << "\n";
    return 0;
}

string

输入数据的每行包含若干个（至少一个）以空格隔开的整数，输出每行中所有整数的和。

#include <iostream>
#include <string> // 慢
#include <sstream> // 更慢

using namespace std;

int main() {
    string line;

    while (getline(cin, line)) {
        int sum = 0, x;
        stringstream ss(line);

        while (ss >> x)
            sum += x;
        cout << sum << "\n";
    }

    return 0;
}

结构体

#include <iostream>

using namespace std;

struct Point
{
    int x, y;
    Point(int x = 0, int y = 0) : x(x), y(y){ // 构造函数
    }
};

Point operator + (const Point& A, const Point& B)
{
    return Point(A.x + B.x, A.y + B.y);
}

ostream& operator << (ostream& out, const Point& p)
{
    out << "(" << p.x << "," << p.y << ")";
    return out;
}

int main()
{
    Point a, b(1, 2);
    a.x = 3;
    cout << a + b << "\n";
    return 0;
}