Answer to Question #242042 in C++ for Alan

Question

Convert the expression into postfix notation and then verify if it is correct or not,direct answers for both 5conversion are not allowed for verification take dummy values for eachvariable.

a+b*(c/d-e)%(f+g*h)-i

Answer 1

#include<bits/stdc++.h>
using namespace std;


int prec(char a) {
	if(a == '^')
		return 3;
	else if(a == '/' || a=='*')
		return 2;
	else if(a == '+' || a == '-')
		return 1;
	else
		return -1;
}


void infix_to_postfix(string s) {


	stack<char> stk; 
	string res;


	for(int i = 0; i < s.length(); i++) {
		char c = s[i];


		if((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9'))
			res += c;


		else if(c == '(')
			stk.push('(');


		else if(c == ')') {
			while(stk.top() != '(')
			{
				res += stk.top();
				stk.pop();
			}
			stk.pop();
		}


		else {
			while(!stk.empty() && prec(s[i]) <= prec(stk.top())) {
				res += stk.top();
				stk.pop();
			}
			stk.push(c);
		}
	}
	while(!stk.empty()) {
		res += stk.top();
		stk.pop();
	}
	cout << res << endl;
}


int main() {
	string expression = "a+b*(c/d-e)%(f+g*h)-i";
	infix_to_postfix(expression);
	return 0;
}