#include "T_Stack.h"
#include <iostream>
#include <string>

typedef std::string String;

int eval_infix(int left, char op, int right)
{
	switch (op)
	{
	case '+': return left + right;
	case '-': return left - right;
	case '*': return left * right;
	case '/': return left / right;
	case '%': return left % right;
	}
	return 0;
}

bool isOperator(char c)
{
	return !((int)c >= (int)'0' && (int)c <= (int)'9');
}

// from char to digit
int char_to_int(char c)
{
	return ((int)c - (int)'0');
}

int eval_postfix(const char expr[])
{
	Stack<int> S;
	int left, right, i = 0;

	int rlt;

	while (expr[i] != '\0')
	{
		if (isOperator(expr[i]))
		{
			right = S.pop();
			left = S.pop();
			rlt=eval_infix(left, expr[i], right);
			S.push(rlt);
		}
		else
		{
			S.push(char_to_int(expr[i]));
		}

		i++;
	}

	return S.pop();

}


// input: fully parenthesized infix expressions
String infix_to_postfix(const char expr[])
{
	Stack <String> S;

	int i = 0;

	String left, right, op, token;

	// (X+Y)  ==> XY+
	while (expr[i] != '\0')
	{
		token = expr[i];
		if (token == ")")
		{
			right = S.pop();
			op = S.pop();
			left = S.pop();
			S.push(left + right + op);	// postfix
		}
		else
		{
			if (token != "(")
			{
				S.push(token);
			}
		}

		i++;
	}

	return S.pop();

}

// input: fully parenthesized infix expressions
String infix_to_prefix(const char expr[])
{
	Stack <String> S;

	int i = 0;

	String left, right, op, token;

	// (X+Y)  ==> +XY
	while (expr[i] != '\0')
	{
		token = expr[i];
		if (token == ")")
		{
			right = S.pop();
			op = S.pop();
			left = S.pop();
			S.push(op + left + right);	// prefix
		}
		else
		{
			if (token != "(")
			{
				S.push(token);
			}
		}

		i++;
	}

	return S.pop();

}

int main()
{
	std::cout << infix_to_postfix("((((2*3)/2)-1)+(3*4))") << std::endl;
	std::cout << infix_to_prefix("((((2*3)/2)-1)+(3*4))") << std::endl;


	std::cout << eval_postfix("23*2/1-34*+") << std::endl;
}