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PostfixEvaluator.c
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PostfixEvaluator.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <ctype.h>
#include <math.h>
#include <stdbool.h>
typedef struct
{
char *data;
int top;
int size;
} Stack;
Stack* initStack(int size)
{
Stack *s = (Stack*)malloc(sizeof(Stack));
s->data = (char*)malloc(sizeof(char) * size);
s->top = -1;
s->size = size;
return s;
}
bool isEmpty(Stack *s)
{
return s->top == -1;
}
bool isFull(Stack *s)
{
return s->top == s->size - 1;
}
void push(Stack *s, char c)
{
if (isFull(s)) {
printf("Stack is full!\n");
return;
}
s->data[++s->top] = c;
}
char pop(Stack *s)
{
if (isEmpty(s)) {
printf("Stack is empty!\n");
return '\0';
}
return s->data[s->top--];
}
char peek(Stack *s)
{
if (isEmpty(s)) {
printf("Stack is empty!\n");
return '\0';
}
return s->data[s->top];
}
int PostfixEvaluator(char* input)
{
int result = 0;
int length = strlen(input);
Stack *s = initStack(length);
for (int i = 0; i < length; i++) {
if (input[i] == ' ' || input[i] == '\t') {
continue;
} else if (isdigit(input[i])) {
push(s, input[i] - '0');
} else {
int op1 = pop(s);
int op2 = pop(s);
switch (input[i]) {
case '+':
result = op1 + op2;
break;
case '-':
result = op2 - op1;
break;
case '*':
result = op1 * op2;
break;
case '/':
result = op2 / op1;
break;
case '^':
result = pow(op2, op1);
break;
}
push(s, result);
}
}
result = pop(s);
free(s);
return result;
}
int main(int argc, char** argv)
{
if (argc != 2) {
printf("Usage: ./PostfixEvaluator \"expression\"\n");
return 1;
}
char* input = argv[1];
int result = PostfixEvaluator(input);
printf("The result is: %d\n", result);
return 0;
}