#include <stdio.h> #include <stdio.h> int main() { double a, b; char f; scanf("%lf %c %lf", &a, &f, &b); //判断部分 if (f == '+' || f == '-' || f == '*' || f == '/') { switch (f) { case '+': printf("%.4lf+%.4lf=%.4f", a, b, a + b); ...