When I run the program it scratches after I convert infix to postfix (In visual studio code, it says: segmentation fault) It works fine, but I cannot debug it. please help me to debug the code.

#include #include #include using namespace std;

class Expression { public: Expression(string input, int direction); // constructor string inToPost(); // method to transform the local infix expression to postfix string postToIn(); // method to transform the local postfix expression to infix double evaluate(); // method to evaluate the expression

private: string infix; // private string variable to store the infix expression string postfix; // private string variable to store the postfix expression

};

Expression::Expression(string input, int direction) {

if (direction == 1) infix = input; else if(direction == 2) postfix = input; }

// inToPost() method

string Expression::inToPost() { stack s; string postfix = ""; // initialize postfix as empty string for (int i = 0; i= 'a' && infix[i] <= 'z') || (infix[i] >= 'A' && infix[i] <= 'Z')) postfix+= infix[i]; // If the scanned character is an '(', push it to the stack. else if (infix[i] == '(')

s.push('(');

else if (infix[i] == ')') { while (s.top() != '(') { postfix += s.top(); s.pop(); } s.pop(); } //If an operator is scanned else { while (!s.empty() && s.top() != '(' && (infix[i] == '*' || infix[i] == '/' || infix[i] == '+' || infix[i] == '-')) { postfix += s.top(); s.pop(); } s.push(infix[i]); } } //Pop all the remaining elements from the stack

while (!s.empty()) { postfix += s.top(); s.pop(); } return postfix; } // postToIn() method string Expression::postToIn() { stack s; for (int i = 0; i= 'a' && postfix[i] <= 'z') || (postfix[i] >= 'A' && postfix[i] <= 'Z')) s.push(string(1, postfix[i])); // If the scanned character is an operator, pop two

// elements from stack apply the operator

else { string val1 = s.top(); s.pop(); string val2 = s.top(); s.pop(); string temp = "(" + val2 + postfix[i] + val1 + ")"; s.push(temp); } } // There must be a single element in stack now which is the result return s.top(); } // evaluate() method takes the local postfix expression and returns the value of the expression.

double Expression::evaluate() { stack s; for (int i = 0; i= 'a' && postfix[i] <= 'z') || (postfix[i] >= 'A' && postfix[i] <= 'Z')) s.push(postfix[i] - '0'); // If the scanned character is an operator, pop two // elements from stack apply the operator else { double val1 = s.top(); s.pop(); double val2 = s.top(); s.pop(); switch (postfix[i]) { case '+': s.push(val2 + val1); break; case '-': s.push(val2 - val1); break; case '*': s.push(val2 * val1); break; case '/': s.push(val2 / val1); break; } } } return s.top();

}

int main() { string input; int direction; cout << "Enter expression in infix or postfix notation: "; cin >> input; cout << "Enter direction (1 for infix to postfix, 2 for postfix to infix): "; cin >> direction; Expression expression(input, direction); if (direction == 1) cout << "Postfix: " << expression.inToPost() << endl; else if (direction == 2) cout << "Infix: " << expression.postToIn() << endl; cout << "Evaluate expression: " << expression.evaluate() << endl; return 0;

}