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#include <stdio.h>
#include <cstdlib>
#include<iostream>
#include<cctype>
#include<cstring>
#include<stack>
#include<cmath>
#include<sstream>
#include <vector>
using namespace std;
class DividedByZero: public exception {};
bool is_balanced(const string& parenthesis)
{
stack<char> store;
char check;
for(string::size_type i = 0; i < parenthesis.length(); ++i)
{
check = parenthesis[i];
if(check == '(' || check == '{' || check == '[')
{
store.push(check);
}
if(!store.empty())
{
if(check == ')')
{
if(store.top() == '(')
{
store.pop();
continue;
}
else
{
break;
}
}
if(check == '}')
{
if(store.top() == '{')
{
store.pop();
continue;
}
else
{
break;
}
}
if(check == ']')
{
if(store.top() == '[')
{
store.pop();
continue;
}
else
{
break;
}
}
}
else
break;
}
return(store.empty());
}
double precedence(char op)
{
if(op == '+' || op == '-')
return 1;
else if(op == '*' || op == '/')
return 2;
return 0;
}
void parse_stack_top(stack<double>& operand, stack<char>& operation)
{
double number1, number2;
number2 = operand.top();
operand.pop();
number1 = operand.top();
operand.pop();
switch(operation.top())
{
case '+': operand.push(number1 + number2);
break;
case '-': operand.push(number1 - number2);
break;
case '*': operand.push(number1 * number2);
break;
case '/':
if(number2 == 0)
{
cout << "\nError!: Divide by zero.";
throw DividedByZero();
}
else
operand.push(number1 / number2);
}
operand.pop();
}
double evaluate_stack(const string& token)
{
stack<double> operand;
stack<char> operation;
for(string::size_type i = 0; i < token.size(); i++)
{
if(isdigit(token[i]) || token[i] == '.')
{
double val;
while(i < token.size() && isdigit(token[i]))
{
val = (val*10) + (token[i]-'0');
i++;
}
i--;
operand.push(val);
}
else if(token[i] == '+' || token[i] == '-' || token[i] == '*' || token[i] == '/')
{
while(!operation.empty() && precedence(token[i]) < precedence(operation.top()))
{
parse_stack_top(operand, operation);
}
operation.push(token[i]);
}
else if(token[i] == '(' || token[i] == '{' || token[i] == '[')
{
operation.push('(');
}
else if(token[i] == ')' || token[i] == '}' || token[i] == ']')
{
while(!operation.empty() && operation.top() != '(' || operation.top() != '{' || operation.top() != '[')
{
parse_stack_top(operand, operation);
}
operation.pop();
}
}
while(!operation.empty())
{
parse_stack_top(operand, operation);
}
return operand.top();
}
int main(int argc, char** argv) {
string token;
cout << "\nYour Expression: ";
getline(cin, token);
if(is_balanced(token))
{
answer = evaluate_stack(token);
cout << "\nResult: " << answer;
}
else
cout << "\nError!: parentheses is not balanced!";
return 0;
}
