W3School TIY Editor

#include <iostream> using namespace std; int main() { int peopleInRoom = 0; cout << "房间内人数：" << peopleInRoom << "\n"; // 3 个人进入 peopleInRoom++; cout << "一人进入。房间内人数：" << peopleInRoom << "\n"; peopleInRoom++; cout << "一人进入。房间内人数：" << peopleInRoom << "\n"; peopleInRoom++; cout << "一人进入。房间内人数：" << peopleInRoom << "\n"; // 1 个人离开 peopleInRoom--; cout << "一人离开。房间内人数：" << peopleInRoom << "\n"; return 0; }