[백준]11723 - 집합(설명X)

#include <cstdio>
#include <cstring>
 
int main() {
    bool arr[21]{ true, };
    int M;
    scanf("%d", &M);
    for (int i = 0; i < M; i++) {
        char str[7];
        scanf("%s", str);
        if (!strcmp(str, "add")) {
            int num;
            scanf("%d", &num);
            arr[num] = true;
        }
        else if (!strcmp(str, "remove")) {
            int num;
            scanf("%d", &num);
            arr[num] = false;
        }
        else if (!strcmp(str, "check")) {
            int num;
            scanf("%d", &num);
            if (arr[0])
                printf("%d\n", arr[num]);
            else
                printf("%d\n", !arr[num]);
        }
        else if (!strcmp(str, "toggle")) {
            int num;
            scanf("%d", &num);
            arr[num] = !arr[num];
        }
        else if (!strcmp(str, "all")) {
            arr[0] = true;
            for (int i = 1; i <= 20; i++)
                arr[i] = true;
        }
        else if (!strcmp(str, "empty")) {
            arr[0] = true;
            for (int i = 1; i <= 20; i++)
                arr[i] = false;
        }
    }
    return 0;
}