#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include "stack.h"
#define MAX_EQU_LEN 100
static int prec(char operator)
{
switch (operator)
{
case '*':
return 5;
case '/':
return 4;
case '%':
return 3;
case '+':
return 2;
case '-':
return 1;
default:
break;
}
return 0;
}
static int isNumeric(char* num)
{
if(atoi(num) == 0)
{
return 0;
}
return 1;
}
char* infix_to_postfix(char* infix)
{
char* postfix = malloc(MAX_EQU_LEN);
stack* s = create_stack();
s->size = strlen(infix);
node* tempPtr = s->stack;
unsigned int i;
char symbol,next;
for(i = 0; i < s->size ; i++)
{
symbol = *((infix + i));
tempPtr = s->stack;
if(isNumeric(&symbol) != 1)
{
strcat(postfix, &symbol);
}
else if(symbol == '(')
{
push(s, symbol);
}
else if(symbol == ')')
{
while(s->size != 0 && top(s) != '(')
{
next = tempPtr->data;
pop(s);
strcat(postfix, &next);
tempPtr = s->stack;
if(tempPtr->data == '(')
{
pop(s);
}
}
}
else
{
while(s->size != 0 && prec(top(s)) > prec(symbol))
{
next = tempPtr->data;
pop(s);
strcat(postfix, &next);
push(s,next);
}
}
while(s->size != 0)
{
next = tempPtr->data;
pop(s);
strcat(postfix, &next);
}
}
return postfix;
}
int evaluate_postfix(char* postfix) {
//For each token in the string
int i,result;
int right, left;
char ch;
stack* s = create_stack();
node* tempPtr = s->stack;
for(i=0;postfix[i] < strlen(postfix); i++){
//if the token is numeric
ch = postfix[i];
if(isNumeric(&ch)){
//convert it to an integer and push it onto the stack
atoi(&ch);
push(s, ch);
}
else
{
pop(&s[i]);
pop(&s[i+1]);
//apply the operation:
//result = left op right
switch(ch)
{
case '+': push(&s[i],right + left);
break;
case '-': push(&s[i],right - left);
break;
case '*': push(&s[i],right * left);
break;
case '/': push(&s[i],right/left);
break;
}
}
}
tempPtr = s->stack;
//return the result from the stack
return(tempPtr->data);
}
此文件是一個程序的一部分,該程序使用堆棧結構來對輸入文件中的後綴執行中綴。其他功能已經過測試並且工作正常,但是當我嘗試添加此部分並實際執行操作時,程序段出現故障。一個調試器說,它發生在infix_to_postfix函數中,但它不會說哪一行,我不知道在哪裏。有誰知道爲什麼這會seg段?從中綴到後綴