Ultima modifica da un moderatore:
Salve recentemente ho scritto un piccolo programma che converte espressioni relativamente semplici dalla notazione infissa ( 3+4) a quella polacca inversa( 3 4 +) . Il programma però mi da strani output , a volte mi da un risultato perfetto altre no altre ancora va in segmentation fault. Non riesco a capire se il problema sia il buffer stdin o cos'altro se qualcuno può illuminarmi gliene sarei molto grato. Allego il codice.
C:
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#define SIZE 55
struct stackNode{
char data;
struct stackNode *nextPtr;
};
typedef struct stackNode StackNode;
typedef StackNode *StackNodePtr;
void push(StackNodePtr *topPtr,char value);
char pop(StackNodePtr *topPtr);
int isOperator(char c);
int precedence(char operator1,char operator2);
void printStack(StackNodePtr currentPtr);
int isEmpty(StackNodePtr topPtr);
char stackTop(StackNodePtr topPtr);
void convertToPostfix(char infix[],char postfix[]);
int main(void){
char infix[SIZE];
char postfix[SIZE];
printf("\nInserisci un 'espressione: ");
char a;
int i=0;
while((a=getchar()) != '\n'){
infix[i] = a;
i++;
}
infix[i]=')';
for(i=0;i<SIZE;i++){
postfix[i]=' ';
}
convertToPostfix(infix,postfix);
putchar('\n');
for(int i=0;i<SIZE;i++){
if(postfix[i] != ' '){
printf("%c ",postfix[i]);}
}
}
void convertToPostfix(char infix[],char postfix[]){
StackNodePtr topPtr = NULL;
char a;
int i=0;
push(&topPtr,'(');
while(isEmpty(topPtr) != 1){
for(i=0;i<SIZE;i++){
if(isdigit(infix[i]) != 0){
postfix[i+1]= infix[i];
}
else if(infix[i] == '('){
push(&topPtr,'(');
}
else if( isOperator(infix[i]) == 1){
a = stackTop(topPtr);
while(isOperator(a)== 1 && precedence(a,infix[i]) != -1){
a = pop(&topPtr);
postfix[i+1] = a;
a = stackTop(topPtr);
}
push(&topPtr,infix[i]);
}
else if( infix[i] == ')'){
int counter =i;
while(topPtr->data != '('){
a= pop(&topPtr);
postfix[counter+1]= a;
counter++;
}
pop(&topPtr);
}
else{
}
}
}
}
char stackTop(StackNodePtr topPtr){
char value;
value = topPtr->data;
return value;
}
int isEmpty(StackNodePtr topPtr){
if(topPtr!=NULL){
return 0;}
else{
return 1;
}
}
void printStack(StackNodePtr currentPtr){
while(currentPtr != NULL){
printf(" %c",currentPtr->data);
currentPtr = currentPtr->nextPtr;
}
}
int precedence(char operator1,char operator2){
switch(operator1){
case '+':
switch(operator2){
case '+':
return 0;
break;
case '-':
return 0;
break;
default:
return -1;
}
break;
case '-':
switch(operator2){
case '+':
return 0;
break;
case '-':
return 0;
break;
default:
return -1;
}
break;
case ('/'):
switch(operator2){
case '+':
return 1;
break;
case '-':
return 1;
break;
case '/':
return 0;
break;
case '*':
return 0;
break;
case '%':
return 0;
break;
default:
return -1;
}
break;
case ('*'):
switch(operator2){
case '+':
return 1;
break;
case '-':
return 1;
break;
case '/':
return 0;
break;
case '*':
return 0;
break;
case '%':
return 0;
break;
default:
return -1;
}
break;
case ('%'):
switch(operator2){
case '+':
return 1;
break;
case '-':
return 1;
break;
case '/':
return 0;
break;
case '*':
return 0;
break;
case '%':
return 0;
break;
default:
return -1;
}
break;
case '^':
return 1;
break;
default :
return 5;
}
}
int isOperator(char c){
switch(c){
case '+' :
return 1;
break;
case '-' :
return 1;
break;
case '*':
return 1;
break;
case '/' :
return 1;
break;
case '%':
return 1;
break;
case '^':
return 1;
break;
default:
return 0;
}
}
void push(StackNodePtr *topPtr,char value){
StackNodePtr newPtr;
newPtr =malloc(sizeof(StackNode));
if(newPtr != NULL){
newPtr->data = value;
newPtr->nextPtr = *topPtr;
*topPtr = newPtr;
}
else{
printf("\nNo memory available");
}
}
char pop(StackNodePtr *topPtr){
StackNodePtr tempPtr;
char popValue;
tempPtr = *topPtr;
popValue = (*topPtr)->data;
*topPtr = (*topPtr)->nextPtr;
free(tempPtr);
return popValue;
}