有如下程序：#include ＜iostream＞using namespace stdclass point{ int x, ypublic: point( int vx, int vy ) { x = vx y = vy } point ( ) x = 0 y= 0 } point operator+( point p1 ) { point p int px = x+ p1.x int py = y + p1.y return point( px, py ) point operator-( point p1 ) { point p int px = x -p1.x int py = y - p1.y return point ( px, py ) } void print() { cout＜＜x＜＜' , '＜＜y＜＜end1 }}int main (){ point p1(10, 10 ), p2( 20, 20 ) p1 = p1 - p2 p1.print () return 0} 执行后的输出结果是