I'm having trouble creating a program that will convert infix to postfix. My code is as follows:
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
#define DEFAULT_SIZE 20
/*
*
*/
class Stack {
char *arr;
int tos, capacity;
public:
//Constructors
Stack();
Stack(int size);
//Destructor
~Stack();
//Methods
void push(char a);
char pop();
int get_size();
bool is_empty();
bool is_full();
void display();
char get_top();
};
Stack::Stack() {
arr = new char[DEFAULT_SIZE];
tos = 0;
capacity = DEFAULT_SIZE;
}
Stack::Stack(int size) {
arr = new char[size];
tos = 0;
capacity = size;
}
Stack::~Stack() {
delete[] arr;
}
void Stack::push(char a) {
if (!is_full())
arr[tos++] = a;
else
cout << "Sorry, the stack is full. Push failed!" << endl;
}
char Stack::pop() {
if (!is_empty())
return arr[--tos];
else {
cout << "Sorry, the stack is empty. Pop failed!" << endl;
return -1;
}
}
char Stack::get_top() {
if (!is_empty())
return arr[tos - 1];
else {
cout << "Sorry, the stack is empty. Pop failed!" << endl;
return 'E';
}
}
int Stack::get_size() {
return tos;
}
bool Stack::is_empty() {
if (tos == 0)
return true;
else
return false;
}
bool Stack::is_full() {
if (tos == capacity)
return true;
else
return false;
}
void Stack::display() {
if (tos == 0)
cout << "The stack is empty" << endl;
else {
for (int i = 0; i<tos;i++)
cout << arr[i] << " ";
cout << endl;
}
}
int main() {
Stack stack(50);
string infix = "(1+3)*2/(6-4)^2";
stringstream ss;
for (char c : infix) {
if ('0' <= c && c <= '9') {
ss << c;
}
else if (c == '(') {
continue;
}
else if (c == ')') {
ss << stack.pop();
stack.pop();
}
else if (c == '^' || c == '*' || c == '/' || c == '+' || c == '-') {
stack.push(c);
}
}
string postfix = ss.str();
cout << postfix;
I know what my issue is, I just dont understand or comprehend how to solve it. This code currently outputs 13+264-2. It needs to output 13+2*64-2^/. I know my issues is with my last else if statement in int main(). I dont understand how to rearrange the operators behind the operands.
Anything in parentheses is passed into the stream correctly, because I can wait until the closing parenthesis is hit to add in the operator. I can't visualize how to make that work for things not in parentheses though. Can anyone offer any advice?
