(074BCT035)_INFIX_TO_POSTFIX_CONVERSION

#include <stdio.h>
#include <ctype.h>
#define size 100
char infix [size] , postfix [size] , stack [size];
int tops = -1,topp = -1,i=0;
int precedence (char x)
{
    if (x=='$')return 3;
    else if (x=='/'|| x=='*')return 2;
    else if (x=='-'||x=='+')return 1;
    else return 0;
}
int main()
{
    FILE *fp;
    fp = fopen("074BCT035_LAB1.txt","a");
    printf("Enter Infix Expression \n");
    fprintf(fp,"\n Student Roll Number :074BCT035 \n Infix To Postfix Expression Coversion \n Enter Infix Expression \n");
    scanf("%s",infix);
    for (i = 0 ; infix [i] != '\0' ; i++)
    {
        if (i==0)
        {
            printf("\n Infix Expression          Stack         Postfix Expression \n");
            fprintf(fp,"%s \n",infix);
            fprintf(fp,"\n Infix Expression          Stack         Postfix Expression \n");
        }
        if (isalnum(infix [i]))
        {
            topp ++;
            postfix [topp] = infix [i];
        }
        else if ( infix [i] == ')' )
        {
        while (stack [tops] != '('){
            topp ++;
            postfix [topp] = stack [tops];
            stack [tops] = ' ';
            tops --;
        }
        tops --;
        }
        else {
            if(precedence(infix[i])<precedence(stack[tops])){
                topp ++;
                postfix [topp] = stack [tops];
                tops -- ;
            }
            else{
                tops ++;
                stack [tops] = infix [i];
            }}
            printf(" %c                         %s                  %s                 \n",infix [i],stack,postfix);
            fprintf(fp," %c                         %s                  %s                 \n",infix [i],stack,postfix);
            }
            if (tops != -1)
            {
                while(tops!=-1){
                topp ++;
                postfix [topp] = stack [tops];
                tops--;
            }}
            /*for (int d = 0; topp>=d ; d++)
        {
            printf(" %c                         %s             %s                 \n",postfix [d]);
        } */
        printf("                           Empty             %s                 \n",postfix);
        fprintf(fp,"                           Empty             %s                 \n",postfix);
        fprintf(fp,"\n");
        fclose(fp);
        return 0;
}