中缀到后缀循环

Question

enter code here,

#include <stdio.h>
#include <ctype.h>

#define SIZE 50
char s[SIZE];
int top=-1;   

void push(char elem)
{                  
    s[++top]=elem;
}

char pop()
{                     
    return(s[top--]);  
}

int pr(char elem)
{                
    switch(elem)
    {
        case '#': return 0;
        case '(': return 1;
        case '+':
        case '-': return 2;
        case '*':
        case '/': return 3;
    }
}

void main()
{                       
    char infx[50],pofx[50],ch,elem;
    int i=0,k=0,j;
    for(j=0;j<=3;j++)
    {
        printf("\n\nRead the Infix Expression ? ");
        scanf("%s",infx);
        push('#');
        while( (ch=infx[i++]) != '\0')
        {
            if( ch == '(') 
                push(ch);
            else
                if(isalnum(ch)) 
                    pofx[k++]=ch;
                else
                    if( ch == ')')
                    {
                        while( s[top] != '(')
                        pofx[k++]=pop();
                        elem=pop();
                    }
                    else
                    {      
                        while( pr(s[top]) >= pr(ch) )
                            pofx[k++]=pop();
                        push(ch);
                    }
        }  

        while( s[top] != '#')    
            pofx[k++]=pop();

        pofx[k]='\0';         
        printf("\n\nGiven Infix Expn: %s  Postfix Expn: %s\n",infx,pofx);
    }
}

When looping through infix to post fix expression,it's not looping beyond 1st loop.

It is producing output of 1st loop and showing segmentation fault for rest of loops

Please can somebody guide me?

Consider an example

given input,

Given Infix Expn: a+b Postfix Expn: ab+

Read the Infix Expression ? ab
Segmentation fault (core dumped)

Answer 1

you need to reset the index for pofx and infx for every new input. ie to reset i and k in the for-loop . Fix as below,

void main()
{                       
    char infx[50],pofx[50],ch,elem;
    int i=0,k=0,j;
    for(j=0;j<=3;j++)
    {
        i=0;j=0;//here is the update

        //rest of your code follows,

    }
}