好玩的一道笔试题

#include <iostream>

int cal(int a,int b, int c){
        int res = 0;
        (!(a^1) && (res = (b+c))) || (!(a^2) && (res = (b-c))) 
        || (!(a^3) && (res = (b*c))) || (!(a^3) && (res = (b/c)));
        printf("res:%d\n", res);
}

int main(){
        int a = 0;
        int b = 5;
        int c = 6;
        printf("b:5,c:6,pls input a:\n");
        while (std::cin >> a)
        cal(a,5,6);
}