我正在尝试用C语言创建一个计算器,可以按照优先级进行计算,并获得正确的结果,例如:
((5+5)/3)*3) -- > 9
((1+2) * 3) -- > 9
我的代码可以计算这些示例。但是对于像这样的表达式
(2+5) * (2+5)
,我的程序会给出错误的答案。
我使用了两个栈,一个用于操作符,一个用于数字。它遵循以下原则:
如下:
((4 - 2) * 5) + 3
--> 正常的中缀表达式:
+ * - 4 2 5 3
伪代码:
Read + (an operation), push it onto the stack,
Read * (an operation), push it onto the stack,
Read - (an operation), push it onto the stack,
Read 4 (a number), the top of the stack is not a number, so push it onto the stack.
Read 2 (a number), the top of the stack is a number, so pop from the stack twice, you get 4 - 2, calculate it (2), and push the result (2) onto the stack.
Read 5 (a number), the top of the stack is a number, so pop from the stack twice, you get 2 * 5, push the result (10) onto the stack.
Read 3 (a number), the top of the stack is a number, so pop from the stack twice, you get 3 + 10, push the result (13) onto the stack.
Nothing left to read, pop from the stack and return the result (13).
实际代码:
#include <stdio.h>
#include<ctype.h>
#include<stdlib.h>
#include<string.h>
#define MAXSIZE 102
typedef struct
{
char stk[MAXSIZE];
int top;
}STACK;
typedef struct stack
{
int stk[MAXSIZE];
int itop;
}INT_STACK;
STACK s;
INT_STACK a;
void push(char);
char pop(void);
void display(void);
int main()
{
a.itop = 0;
char string[MAXSIZE],vyb,vyb2;
int cislo1,cislo2,vysledok;
while (gets(string) != NULL){
for(int j = strlen(string); j > 0; j--){
if(string[j] == '*' || string[j] == '/' || string[j] == '+' || string[j] == '-')
push(string[j]);
}
//display();
for(int j = 0; j < strlen(string); j++){
if(isdigit(string[j])&&!(a.itop)){
//display();
char pomoc[2];
pomoc[0] = string[j];
pomoc[1] = '\0';
int_push(atoi(pomoc));
}
else if(isdigit(string[j])&&(a.itop)){
cislo1 = int_pop();
vyb2 = pop();
char pomoc[2];
pomoc[0] = string[j];
pomoc[1] = '\0';
cislo2 = atoi(pomoc);
if(vyb2 == '+')
vysledok = cislo1+cislo2;
else if(vyb2 == '-')
vysledok = cislo1-cislo2;
else if(vyb2 == '*')
vysledok = cislo1*cislo2;
else if(vyb2 == '/')
vysledok = cislo1 / cislo2;
//printf(" v %d",vysledok);
int_push(vysledok);
}
}
printf("%d\n",int_pop());
}
}
/* Function to add an element to the stack */
void push (char c)
{
s.top++;
s.stk[s.top] = c;
//printf ("pushed element is = %c \n", s.stk[s.top]);
}
/* Function to delete an element from the stack */
char pop ()
{
char num = s.stk[s.top];
// printf ("poped element is = %c\n", s.stk[s.top]);
s.top--;
return(num);
}
int empty()
{
if (s.top == - 1)
{
printf ("Stack is Empty\n");
return (s.top);
}
return 1;
}
void display ()
{
int i;
if (!empty)
{
printf ("Stack is empty\n");
return;
}
else
{
printf ("\n The status of the stack is \n");
for (i = s.top; i >= 0; i--)
{
printf ("%c\n", s.stk[i]);
}
}
printf ("\n");
}
void int_push (int c)
{
a.itop++;
a.stk[a.itop] = c;
//printf ("pushed element is = %d \n", a.stk[a.itop]);
}
/* Function to delete an element from the stack */
int int_pop ()
{
int num = a.stk[a.itop];
// printf ("poped element is = %d\n", a.stk[a.itop]);
a.itop--;
return(num);
}
有没有其他的方法可以创建一个可以给出正确答案的优先级计算器?
感谢您的回复
3-(2-1)
。 - CiaPan