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  1. #include <iostream>
  2. #include <stack>
  3. #include <string>
  4.  
  5. using namespace std;
  6.  
  7. int precedence(char op) {
  8.     if (op == '+' || op == '-')
  9.         return 1;
  10.     if (op == '*' || op == '/')
  11.         return 2;
  12.     return 0;
  13. }
  14.  
  15. string infixToPostfix(const string& infix) {
  16.     string postfix;
  17.     stack<char> operators;
  18.  
  19.     for (char c : infix) {
  20.         if (isalnum(c)) {
  21.             postfix += c;
  22.         } else if (c == '(') {
  23.             operators.push(c);
  24.         } else if (c == ')') {
  25.             while (!operators.empty() && operators.top() != '(') {
  26.                 postfix += operators.top();
  27.                 operators.pop();
  28.             }
  29.             if (!operators.empty() && operators.top() == '(')
  30.                 operators.pop();
  31.         } else {
  32.             while (!operators.empty() && precedence(operators.top()) >= precedence(c)) {
  33.                 postfix += operators.top();
  34.                 operators.pop();
  35.             }
  36.             operators.push(c);
  37.         }
  38.     }
  39.  
  40.     while (!operators.empty()) {
  41.         postfix += operators.top();
  42.         operators.pop();
  43.     }
  44.  
  45.     return postfix;
  46. }
  47.  
  48. int main() {
  49.     string infix_expression;
  50.     cout << "Enter infix expression: ";
  51.     getline(cin, infix_expression);
  52.  
  53.     string postfix_expression = infixToPostfix(infix_expression);
  54.     cout << "Postfix expression: " << postfix_expression << endl;
  55.  
  56.     return 0;
  57. }
  58.  
Success #stdin #stdout 0.01s 5308KB
comments (?)
stdin 
Standard input is empty
stdout 
Enter infix expression: Postfix expression:
https://ideone.com/XU0xBr
language:
C++ (gcc 8.3)
created:
19 days ago
visibility:
public

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