Hi all, this is my fist post here and I am a beginner at C programming.
I have the following code for converting a list of t infix expressions into their postfix form:-

Code:
  1. #include<stdio.h>
  2. #include<string.h>
  3. #include<ctype.h>
  4. #define MAX 400
  5. struct stack
  6. {
  7.     char arr[MAX];
  8.     int top;
  9. };
  10. void initstack(struct stack *);
  11. void push(struct stack *,char);
  12. char pop(struct stack *);
  13. void convert(struct stack *s,char *);
  14. int priority(char e);
  15. int main()
  16. {
  17.    int t,k=0;
  18.    char str[MAX];
  19.    struct stack s1;
  20.    scanf("%d",&t);          //No of infix expressions to be converted in postfix//
  21.    initstack(&s1);
  22.    while(t)
  23.    {
  24.        t--;
  25.        scanf("%s",str);
  26.        convert(&s1,str);
  27.    }
  28.    return 0;
  29. }
  30. void initstack(struct stack *s)
  31. {
  32.     s->top=-1;
  33. }
  34. void push(struct stack *s,char data)
  35. {
  36.     if(s->top==MAX-1)
  37.      return;
  38.     else
  39.     {
  40.         s->top++;
  41.         s->arr[s->top]=data;
  42.     }
  43. }
  44. char pop(struct stack *s)
  45. {
  46.     char a;
  47.     if(s->top==-1)
  48.      return -1;
  49.     else
  50.     {
  51.         a=s->arr[s->top];
  52.         s->top--;
  53.         return a;
  54.     }
  55. }
  56. void convert(struct stack *s,char *exp)
  57. {
  58.     char op[400],d,p1;
  59.     int i=0,j=0,pr;
  60.     while(*(exp))
  61.     {
  62.         if(*(exp)=='(')
  63.          {
  64.           push(s,*(exp));
  65.           exp++;
  66.          }
  67.         else if(*(exp)=='+'||*(exp)=='-'||*(exp)=='^'||*(exp)=='/'||*(exp)=='*')
  68.          {
  69.            if(s->top==-1)
  70.             {
  71.                 push(s,*(exp));
  72.                 exp++;
  73.             }
  74.             else
  75.             {
  76.                 p1=pop(s);
  77.                 if(priority(p1)<priority(*(exp)))
  78.                 {
  79.                     push(s,p1);
  80.                     push(s,*(exp));
  81.                     exp++;
  82.                 }
  83.                 else
  84.                 {
  85.                     while(priority(p1)>=priority(*(exp)))
  86.                     {
  87.                       op[i]=p1;
  88.                       i++;
  89.                       p1=pop(s);
  90.                     }
  91.                     push(s,p1);
  92.                     push(s,*(exp));
  93.                     exp++;
  94.                 }
  95.             }
  96.           }
  97.           else if(*(exp)==')')
  98.           {
  99.               p1=pop(s);
  100.               while((p1)!='(');
  101.               {
  102.                   op[i]=p1;
  103.                   i++;
  104.                   p1=pop(s);
  105.               }
  106.               exp++;
  107.            }
  108.            else if(isalpha(*(exp)))
  109.            {
  110.                while(isalpha(*(exp)))
  111.                {
  112.                op[i]=*(exp);
  113.                exp++;
  114.                i++;
  115.                }
  116.             }
  117.         }
  118.         while(s->top!=-1)
  119.         {
  120.             d=pop(s);
  121.             op[i]=d;
  122.             i++;
  123.         }
  124.         op[i]='\0';
  125.         while(op[j])
  126.         printf("%c",op[j++]);
  127.         printf("\n");
  128. }
  129. int priority(char e)
  130. {
  131.     if(e=='^')
  132.      return 3;
  133.     else if(e=='*'||e=='/')
  134.      return 2;
  135.     else if(e=='+'||e=='-')
  136.      return 1;
  137.     else
  138.      return 0;
  139. }
I am getting correct outputs for non-bracketed inputs.But for bracketed
inputs I don't get any output. I have checked the code many times but
couldn't find as to why there is no output for bracketed inputs.Please
help