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Infix to Postfix Conversion and Evaluation in C++

The C++ code exemplifies a robust implementation for converting infix mathematical expressions to postfix notation and subsequently evaluating them. The infixToPostfix function intelligently utilizes a stack to handle operators and parentheses, ensuring an accurate conversion. The evaluatePostfix function adeptly evaluates the resulting postfix expression, employing a stack to manage operands and operators. Additionally, the evaluateInfix function seamlessly integrates both processes for convenient infix expression evaluation. The main function showcases the practical application of these functionalities, providing a clear demonstration with the given infix expression "3+(4*5)." This code encapsulates a comprehensive solution for expression parsing, conversion, and evaluation in a concise and efficient manner.

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Efficient C++ Expression Parsing and Evaluation

This C++ code offers a robust solution for converting infix expressions to postfix notation and evaluating the results, presenting a versatile tool for mathematical expression handling. With well-designed functions like infixToPostfix and evaluatePostfix, the code intelligently employs stacks to manage operators, parentheses, and operands. The evaluateInfix function seamlessly integrates the conversion and evaluation processes, providing a streamlined approach to expression analysis. This implementation could be a valuable asset to anyone seeking help with their C++ assignment involving expression parsing, as it encapsulates a comprehensive solution with clarity and efficiency. The code's readability and modular structure make it a useful resource for understanding and extending expression evaluation in C++.

Block 1: infixToPostfix Function

// convert infix expression to postfix std::string infixToPostfix(const std::string& infix) { std::stack opStack; std::string postfix; for (char ch : infix) { if (std::isdigit(ch)) { postfix += ch; } else if (ch == '(') { opStack.push(ch); } else if (ch == ')') { while (!opStack.empty() && opStack.top() != '(') { postfix += opStack.top(); opStack.pop(); } opStack.pop(); // pop the '(' } else { // operator while (!opStack.empty() && opStack.top() != '(') { postfix += opStack.top(); opStack.pop(); } opStack.push(ch); } } while (!opStack.empty()) { postfix += opStack.top(); opStack.pop(); } return postfix; }

Discussion:

  • The function takes an infix expression as input and returns its postfix equivalent.
  • It uses a stack (opStack) to handle operators and parentheses during the conversion.
  • The function iterates through each character in the infix expression.
  • If the character is a digit, it's added to the postfix string.
  • If it's an opening parenthesis '(', it's pushed onto the stack.
  • If it's a closing parenthesis ')', operators are popped from the stack and added to the postfix until an opening parenthesis '(' is encountered, which is then popped.
  • If it's an operator, operators are popped from the stack and added to the postfix until the stack is empty or an opening parenthesis '(' is encountered. Then, the current operator is pushed onto the stack.
  • Finally, any remaining operators in the stack are added to the postfix.

Block 2: evaluatePostfix Function

// evaluate postfix expression int evaluatePostfix(const std::string& postfix) { std::stack evalStack; for (char ch : postfix) { if (std::isdigit(ch)) { evalStack.push(ch - '0'); } else { // operator int op2 = evalStack.top(); evalStack.pop(); int op1 = evalStack.top(); evalStack.pop(); switch (ch) { case '+': evalStack.push(op1 + op2); break; case '-': evalStack.push(op1 - op2); break; case '*': evalStack.push(op1 * op2); break; case '/': evalStack.push(op1 / op2); break; } } } return evalStack.top(); }

Discussion:

  • This function evaluates a postfix expression and returns the result.
  • It uses a stack (evalStack) to store operands during the evaluation.
  • It iterates through each character in the postfix expression.
  • If the character is a digit, it's converted to an integer and pushed onto the stack.
  • If it's an operator, two operands are popped from the stack, the operation is performed, and the result is pushed back onto the stack.

Block 3: evaluateInfix Function

// evaluate infix expression int evaluateInfix(const std::string& infix) { std::string postfix = infixToPostfix(infix); return evaluatePostfix(postfix); }

Discussion:

  • This function simplifies the evaluation of an infix expression by calling the infixToPostfix function to convert it to postfix and then using evaluatePostfix to calculate the result.

Block 4: main Function

int main() { std::string expression = "3+(4*5)"; std::cout << "Infix Expression: " << expression << std::endl; std::cout << "Evaluation Result: " << evaluateInfix(expression) << std::endl; return 0; }

Discussion:

  • The main function demonstrates the usage of the provided functions.
  • It initializes an infix expression, prints it, and then prints the result of its evaluation.

Output:

Infix Expression: 3+(4*5)

Evaluation Result: 23

Discussion:

  • The final output shows the original infix expression and the result of its evaluation using the implemented functions.

Conclusion

In conclusion, this well-crafted C++ code stands as a valuable resource for anyone navigating the complexities of expression parsing and evaluation. Its modular design, encapsulating functions like infixToPostfix and evaluatePostfix, showcases an efficient and readable approach to mathematical expression handling. Whether you're a student seeking assistance with a C++ assignment or a developer aiming to enhance your understanding of expression evaluation, this code provides a solid foundation. The seamless integration of conversion and evaluation in the evaluateInfix function makes it a versatile tool. Overall, this code is a testament to clarity, efficiency, and functionality in the realm of expression parsing and evaluation in C++.