用栈求无括号表达式，求大神来帮忙，很迷茫

#include<stdio.h>
#include<malloc.h>
#define maxsize 100
typedef struct node
{
char stact[maxsize];
int top;
}*seqstact;
int initstact(seqstact s)
{
if((s=(seqstact)malloc(sizeof(struct node)))==NULL) return 0;
s->top=-1;
return 1;
}
int push(seqstact s,char x)
{
if(s->top>=maxsize-1) return 0;
s->top++;
s->stact[s->top]=x;
return 1;
}
int pop(seqstact s,char ch)
{
if(s->top<0) return 0;
ch=s->stact [s->top ];
s->top --;
return (ch);
}
int gettop(seqstact s)
{
if(s->top<0) return 0;
return (s->stact[s->top]);
}
int empty(seqstact s)
{
if(s->top<0)return 1;
else
return 0;
}
int In(char ch)
{
if(ch=='+'||ch=='-'||ch=='*'||ch=='/')
return 1;
else
return 0;
}
int operate(int a,char theta,int b)
{
if(theta=='+')
return (a+b);
if(theta=='-')
return(a-b);
if(theta=='*')
return (a*b);
if(theta=='/')
return(a/b);

}
char Precede(char a,char b)
{
char c;
if(a=='#'&&(b=='+'||b=='-'||b=='*'||b=='/'))
{
c='>';
return (c);
}
if((a=='+'||a=='-')&&(b=='*'||b=='/'))
{
c='<';
return (c);
}
if((a=='*'||a=='/')&&(b=='+'||b=='-'))
{
c='>';
return (c);
}
if((a=='+'||a=='-')&&(b=='+'||b=='-'))
{
c='=';
return (c);
}
if((a=='*'||a=='/')&&(b=='+'||b=='-'))
{
c='=';
return (c);
}
}
int main()
{
int a,b,v,temp;
char theta;
char ch; //ch用于保存读入表达式的字符
seqstact optr,opnd; //OPTR运算符栈，OPND运算数栈
initstact(optr);initstact(opnd);
push(optr,'#');
ch=getchar();
while(ch!='#'||gettop(optr)!='#')
{
if(!In(ch)) //用于判断字符是否为运算符，是运算符返回1，是操作数返回0
{
{
//存放数字的临时变量
temp=ch-'0'; //将字符转换为十进制数
ch=getchar();
}
while(!In(ch))
{
temp=temp*10+ch-'0';ch=getchar(); //将每个读入的操作数各位转化为十进制数
}
push(opnd,temp); //不是运算符的进栈
}
else
{
switch(Precede(gettop(optr),ch))
{
case'<':push(optr,ch);ch=getchar();break;
case'=':pop(optr,ch);ch=getchar();break;
case'>':pop(optr,theta);pop(opnd,b);pop(opnd,a);
push(opnd,operate(a,theta,b));break;
}
v=gettop(opnd);
printf("%d\n",v);
}
}
return 0;
}