现在只是测试阶段
我想问问这段代码有什么问题：（为什么一运行输入后就无响应）
各位看看哪里可以改一下
#include <stdio.h>

int main()
{
        char ch[20];
        int j,i,a[40],num[21];
        
        for(i=1;i<10;++i)
        {
                scanf("%d",&num[i]);
                if(getchar()=='.')
                {
                        a[i*2-1] = '.';
                        break;
                }
                else
                scanf("%c",&a[i*2-1]);
                scanf("%c",&ch[i]);
                scanf("%c",&a[i*2]);
               
        }
        
        for(i=1;;i++)
        {
                if(a[i*2] == '(')
                {
                        switch(ch[i+1])
                        {
                        case '+':
                                {
                                        num[i+1] += num[i+2];
                                        ch[i+1] = '+';
                                        num[i+2] = 0;
                                }
                        case '-':
                                {
                                        num[i+1] -= num[i+2];
                                        ch[i+1] = '+';
                                        num[i+2] = 0;
                                }
                        }
                }
                if(a[i*2-1] == '.')
                        break;
        }
        
        for(j=0;j<20;j++)
        {
                for(i=1;;i++)
                {
                        if(a[i*2-1] == '.')
                                break;
                        switch(ch[i])
                        {
                        case '+':
                                {
                                        num[i] += num[i+1];
                                        ch[i+1] = '+';
                                        num[i+1] = 0;
                                }
                        case '-':
                                {
                                        num[i] -= num[i+1];
                                        ch[i+1] = '+';
                                        num[i+1] = 0;
                                }
                        }
                }
        }
        
        printf("%d",num[1]);
        
        return 0;
}

不是呀，我是按“数字（空格或括号）运算符号（空格或括号）数字”输入的，然后多个式子后以结束符结尾的，例如"1 + "就是一次循环

哦，先改一改