C 新手/不明白问题可能是什么

Question

自从我学习 C 语言以来，我决定制作一个简单的程序，用于加、减和计算两个变量的乘积。根据用户的输入是1,2还是3来选择加/减/折叠。

#include <stdio.h>

int main (void) {
   int a, b, c, d, e, f, g;
   a=19;   b=11;  c=a+b;  d=a-b;  e=a*b;  f=-1;

   while (f<0 && f>3) {
      printf("-press 1 to calculate the sum of a and b\n");
      printf("-press 2 to calculate the difference between a and b\n");
      printf("-press 3 to calculate the product of a and b\n");

      scanf("%d\n",&g);
      f=g;
      return;
   }

   if (f == 1) {
      printf("A+B= %ls\n", &c);
   } else if (f == 2) {
      printf("A-B= %ls\n", &d);
   } else if (f == 3) {
      printf(" A*B= %ls\n", &e);
   }
return 0;
} 

When i run the program its reads "g" and then it stops. any suggestions to why is this happening btw i also tried removing the while statement.

Answer 1

我认为你的意思是下面的 while 循环

while ( f < 0 || f > 3 )
{
     printf("-press 1 to calculate the sum of a and b\n");
     printf("-press 2 to calculate the difference between a and b\n");
     printf("-press 3 to calculate the product of a and b\n");
     scanf( "%d", &g );
     f = g;
}

即注意1)while循环的条件，2)删除return语句，3)删除scanf中的字符'\n'，因为它是多余的。

并且在 printf 调用中删除运算符 & 并使用转换说明符 %d。

 if ( f == 1 ) {
  printf(" A+B= %d\n", c) ;
 }
 else if ( f == 2) {
  printf(" A-B= %d\n", d );
 }
 else if ( f == 3 ) {
  printf(" A*B= %d\n",e );
 }