Lecture 244:- Student Challenge Infix to Postfix with Associativity and Parenthesis

Let's modify the Infix to Postfix conversion code to handle associativity and parentheses. Infix expressions may have left-associative and right-associative operators, and we also need to ensure that the parentheses are correctly handled during the conversion.

Below is the C++ implementation of Infix to Postfix conversion with associativity and parentheses support:

cppCopy code

#include <iostream> #include <stack> #include <string> #include <cctype> int precedence(char op) {    if (op == '+' || op == '-')        return 1;    else if (op == '*' || op == '/')        return 2;    return 0; } bool isLeftAssociative(char op) {    return op == '+' || op == '-' || op == '*' || op == '/'; } std::string infixToPostfix(const std::string& infix) {    std::stack<char> operatorStack;    std::string postfix;    for (char c : infix) {        if (std::isspace(c)) {            continue; // Skip whitespaces        } else if (std::isalnum(c)) {            postfix += c; // Operand, append to postfix string        } else if (c == '(') {            operatorStack.push(c);        } else if (c == ')') {            while (!operatorStack.empty() && operatorStack.top() != '(') {                postfix += ' '; // Add a space between consecutive operands                postfix += operatorStack.top();                operatorStack.pop();            }            operatorStack.pop(); // Pop and discard the opening parenthesis        } else { // Operator            while (!operatorStack.empty() && operatorStack.top() != '(' &&                   ((isLeftAssociative(c) && precedence(operatorStack.top()) >= precedence(c)) ||                    (!isLeftAssociative(c) && precedence(operatorStack.top()) > precedence(c)))) {                postfix += ' '; // Add a space between consecutive operands                postfix += operatorStack.top();                operatorStack.pop();            }            postfix += ' '; // Add a space between consecutive operands            operatorStack.push(c);        }    }    while (!operatorStack.empty()) {        postfix += ' '; // Add a space between consecutive operands        postfix += operatorStack.top();        operatorStack.pop();    }    return postfix; } int main() {    std::string infix, postfix;    std::cout << "Enter an infix expression: ";    std::getline(std::cin, infix);    postfix = infixToPostfix(infix);    std::cout << "Postfix expression: " << postfix << std::endl;    return 0; }

In this implementation, we added a isLeftAssociative function to check if an operator is left-associative. This function helps us decide the associativity of the operators during the conversion process.

Additionally, we modified the condition in the while loop for handling operators in the infixToPostfix function. Now, it takes into account the associativity and precedence of the operators while populating the postfix string.

This code will correctly handle left-associative and right-associative operators, and also take care of parentheses in the infix expression during the conversion to postfix.