我正在解决一个练习,其中一个函数必须将中缀表示法转换为后缀表示法。下面是我的整个代码
#include<stdio.h>
#define MAX 100
char stack[MAX];
int top;
void compact(char Descomp[], char Compac[]);
void init_stack();
int push(char Elem);
int desempilha(char *Elem);
int priority(char Operator);
int arity(char Exp[], int position);
int translate_pos(char exp[], char exp_pos[]);
int main()
{
char Exp[MAX]; /* stores the expression read from stdin */
char Exp_compact[MAX]; /* stores expression without spaces */
char Exp_pos[MAX]; /* stores the expression after the translation for postfix*/
int indicator; /* indicate if an error occurred, 0 for NO ERROR and -1 for ERROR*/
indicator = 0;
printf("\nType the expression: ");
gets(Exp);
compact(Exp, Exp_compact);
indicator = translate_pos(Exp_compact, Exp_pos);
puts(Exp_pos);
return indicator;
}
/* compact function delete spaces within the expression read from stdin */
void compact(char Descomp[], char Compac[])
{
int i;
int j;
i = 0;
j = 0;
while(Descomp[j] != '\0')
{
if(Descomp[j] != ' ')
{
Compac[i] = Descomp[j];
i++;
}
j++;
}
}
/* initiate the stack by setting top = -1 */
void init_stack()
{
top = -1;
}
/* puts the element Elem in the stack */
int push(char Elem)
{
if(top == MAX - 1) /* Stack is full */
return -1;
top++;
stack[top] = Elem;
return 0;
}
/* remove the element in stack[top] and puts it in &Elem*/
int pop(char *Elem)
{
if(top == -1) /* stack is empty */
return -1;
*Elem = stack[top];
top--;
return 0;
}
/* Return the priority of an operator */
int priority(char Operator)
{
switch(Operator)
{
case '+': return 1;
case '-': return 1;
case '*': return 2;
case '/': return 2;
case '^': return 3;
case '(': return 4;
case ')': return 5;
default : return 0;
}
}
/* returns the arity of CONSTANTS + - * / and ^, for ( an ) is merely symbolic */
int arity(char Exp[], int position)
{
if(priority(Exp[position]) == 1)
{
if( (position == 0) || ( (priority(Exp[position - 1]) >= 1) && (priority(Exp[position - 1]) <= 3) ))
return 1;
else
return 2;
}
else if( (priority(Exp[position]) > 1) && (priority(Exp[position]) <= 4))
return 2;
else
return priority(Exp[position]);
}
/* reads an infix expression and returns postfix expression */
int translate_pos(char exp[], char exp_pos[])
{
int i;
int j;
int ind;
char trash;
i = 0;
j = 0;
ind = 0;
trash = ' ';
init_stack();
while(exp[i]!= '\0')
{
if(arity(exp, i) == 0)
{
exp_pos[j] = exp[i];
j++;
}
if(arity(exp, i) == 1)
{
switch(exp[i])
{
case '-':
{
exp_pos[j] = exp_pos[i];
j++;
}
case '+': trash = exp_pos[i];
}
}
if(arity(exp, i) == 2)
{
while((top != -1) && (priority(stack[top]) <= priority(exp[i])))
{
ind = pop(&exp_pos[j]);
j++;
}
ind = push(exp[i]);
}
if(priority(exp[i]) == 4)
{
ind = push(exp[i]);
}
if(priority(exp[i]) == 5)
{
while( (top != -1) && (stack[top] != '('))
{
ind = pop(&exp_pos[j]);
j++;
}
if(stack[top] == '(')
ind = pop(&trash);
}
i++;
}
while(top != -1)
{
ind = pop(&exp_pos[j]);
j++;
}
return ind;
}
我用来翻译表达式的算法是
while there is token to be read;
read the token;
if token is a constant
push it to Exp_Postfix;
if token is '('
push it to stack
if token is ')'
pop from the stack all symbols until '(' be find and remove '(' from the stack
if token is an operator and its arity is 2
pop all operators with less or equal priority than the token and store then in the Exp_Postfix;
push token to the stack;
if token is an operator and its arity is 1
if token is '-'
push it to Exp_postfix;
if token is '+'
pass to the next token;
pop all remaining symbols in the stack and push then, in order, to the Exp_Postfix;
我编译了 .c 存档使用
gcc -Wall archive.c -o archive
并执行它。我给表情
5+(6*9^14)
它返回的表达式是
5
如果错误出现在我的代码中或问题的解决方案中,我现在不这样做。