必须充分掌握struct的使用，包括其构造和重载函数的写法：
#include <iostream>
using namespace std;
struct node {
int x, y;
node(){
}
// node (int x, int y){
// this->x = x;
// this->y = y;
// }
node (int x, int y) : x(x), y(y){
}
node operator + (const node s){
node rt;
rt.x = this->x + s.x;
rt.y = this->y + s.y;
return rt;
}
node operator * (const node s){
node rt;
rt.x = this->x * s.x;
rt.y = this->y * s.y;
return rt;
}
bool operator ==(const node s){
if(s.x == this->x && s.y == this->y){
return 1;
}
else{
return 0;
}
}
bool operator < (const node s){
if(this->x < s.x){
return 1;
}
else{
return 0;
}
}
};
int main(){
node a, b;
a.x = a.y = 1;
b.x = b.y = 3;
a = a + b;
cout << "a: " << a.x << " " << a.y << endl;
node c(1, 3);
cout << "c: " << c.x << " " << c.y << endl;
node d = c;
cout << "d: " << d.x << " " << d.y << endl;
if(d == c){
cout << "d = c" << endl;
}
if(a < c){
cout << "a < c" << endl;
}
else{
cout << "a !< c" << endl;
}
return 0;
}