W3School TIY Editor

#include <stdio.h> int main() { int peopleInRoom = 0; // 3 个人进入 peopleInRoom++; peopleInRoom++; peopleInRoom++; printf("%d\n", peopleInRoom); // 3 // 1 个人离开 peopleInRoom--; printf("%d\n", peopleInRoom); // 2 return 0; }