Hey guys, I'm having much difficulties with a problem from my C book. The problem asks you to convert an infix notation, such as "1 + 2" to the more computer friendly postfix, "1 2 +". I tried with the algorithm that my book supplied to me but my program keeps crashing. Here's what i have so far:
Thanks for any help guys.Code:#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#define LENGTH(x) ( sizeof(x) / sizeof(x[0]) )
typedef struct node{
char data;
struct node *next;
} Node;
void push( Node **sHead, char value );
char pop( Node **sHead );
int isEmpty( Node *head );
void printS( Node *s );
char stackTop( Node *s );
void convertInToPost( Node **sHead, char *infix, char *postfix );
void strchar( char *str, char c );
int isOperator( char c );
int precedence( char op1, char op2 );
int main( void ){
Node *head = NULL;
char infix[] = "1+2";
char postfix[10];
postfix[0] = '\0';
convertInToPost( &head, infix, postfix );
printf( "%s ", postfix );
return 0;
} // main
void convertInToPost( Node **sHead, char *infix, char *postfix ){
int i;
push( sHead, '(' );
strncat( infix, ")", 1 );
while( !isEmpty( *sHead ) )
for( i = 0 ; i < LENGTH( infix ) ; i++ )
if( isdigit(infix[i]) )
strchar( postfix, infix[i] );
else if( infix[i] == '(' )
push( sHead, infix[i] );
else if( isOperator( infix[i] ) ){
if( precedence( stackTop( *sHead ), infix[i] ) >= 0 )
strchar( postfix, pop( sHead ) );
push( sHead, infix[i] );
}else if( infix[i] == ')' ){
while( stackTop( sHead ) != '(' )
strchar( postfix, pop( sHead ) );
pop( sHead );
}
} // convertIntoPost
void strchar( char *str, char c ){
while( *str != '\0' )
str++;
*str = c;
*(str + 1 ) = '\0';
} // strchar
int isOperator( char c ){
if( c == '*' || c == '/' || c == '+' || c == '-' )
return 1;
return 0;
} // isOperator
int precedence( char op1, char op2 ){
switch( op1 ){
case '*': case '/':
if( op2 == '*' || op2 == '/' )
return 0;
else
return 1;
case '+': case '-':
if( op2 == '*' || op2 == '/' )
return -1;
else
return 0;
}
return -10;
} // precedence
char stackTop( Node *s ){
if( !isEmpty( s ) )
return s->data;
return '\0';
} // stackTop
void printS( Node *s ){
while( !isEmpty( s ) ){
printf( "%3c --> ", s->data );
s = s->next;
}
printf( "NULL\n\n" );
} // printS
void push( Node **sHead, char value ){
Node *newNode;
newNode = malloc( sizeof( Node ) );
if( newNode != NULL ){
newNode->data = value;
newNode->next = *sHead;
*sHead = newNode;
}else
printf( "***ERROR*** Could _NOT_ allocate memory for new object!\n" );
} // push
char pop( Node **sHead ){
Node *temp;
char value;
if( !isEmpty( *sHead ) ){
value = (*sHead)->data;
temp = *sHead;
*sHead = (*sHead)->next;
free( temp );
return value;
}
return '\0';
} // pop
int isEmpty( Node *head ){
return head == NULL;
} // isEmpty
Dat
