[C++] Custom sort

----------------- test.h --------------------#ifndef _TEST_H_ #define _TEST_H_ #include using namespace std; class XY { private: int _x, _y, _value; public: XY() {}; XY(int x, int y, int value) { _x = x; _y = y; _value = value; } ~XY() {} int X() const { return _x; } int Y() const { return _y; } int value() const { return _value; } void SetValues(int x, int y, int value) { _x = x; _y = y; _value = value; } // < operator overloading // x-coordination has first priority, then y-coordingation bool operator<(const XY &xy) const; friend const ostream& operator<<(ostream &os, const XY &xy); }; #endif ------------------- test.cpp ---------------------- #include "test.h" using namespace std; bool XY :: operator<(const XY &xy) const { if( _x < xy.X() ) return true; else if( _x == xy.X() ) { if( _y < xy.Y() ) return true; else return false; } return false; } const ostream& operator<<(ostream &os, const XY &xy) { os << "(" << xy._x << "," << xy._y << ") -> " << xy._value ; return os; } ----------------------- main.cpp -------------------------- #include "test.h" #include #include using namespace std; int main() { vector vec_xy; XY t; t.SetValues(1,1,1); vec_xy.push_back(t); t.SetValues(2,2,4); vec_xy.push_back(t); t.SetValues(1,2,3); vec_xy.push_back(t); t.SetValues(2,1,3); vec_xy.push_back(t); for( int i = 0 ; i < vec_xy.size() ; i++ ) { cout << vec_xy[i] << endl; } cout << "---------- sort -------------" << endl; sort(vec_xy.begin(), vec_xy.end()); for( int i = 0 ; i < vec_xy.size() ; i++ ) { cout << vec_xy[i] << endl; } }