Infixe à postfixer concaténation de chiffres ou de lettres

Question

travaillant sur un programme qui convertit la notation infixe en postfix. Je l'ai pour la plupart des cas sauf lorsque la concaténation de caractères est requise. Par exemple, si je passe une chaîne de nombres (1002 + 304), elle sort 1, 0, 0, 2, 3, 0, 4, + au lieu de 1002, 304, +.

import java.util.*; 


public class InfixToPostfix { 

    private Deque<String> postfix; // Used as a queue of String 


    private static boolean isOperator(char op) 
    { 
     if(op=='+'||op=='-'||op=='*'||op=='/'||op=='^' 
       ||op=='('||op==')') 
     { 
      return true; 
     } 
     return false; 
    } 

    private static boolean lowerEqualPrec(char op1, char op2) 
    { 
     boolean flag = false; 
     if(op1=='+'|| op1=='-') 
     { 
      if(op2=='+'||op2=='-'||op2=='*'||op2=='/'||op2=='^') 
      { 
       flag= true; 
      } 
     }else if(op1=='*' || op1=='/') 
     { 
      if(op2=='*'||op2=='/'||op2=='^') 
      { 
       flag= true; 
      } 
     }else if(op1=='^') 
     { 
      flag= false; 
     }else if(op1=='(') 
     { 
      flag= false; 
     } 
     return flag; 
    } 

    public InfixToPostfix(String infix) 
    { 
     for(int i=0; i<infix.length(); i++) 
     { 
      if(infix.length() ==0 || infix.charAt(0)==')' || 
        infix.charAt(i)=='&' || infix.charAt(infix.length()-1)=='(') 
      { 
       throw new IllegalArgumentException(); 
      } 
     } 

     postfix = new LinkedList<String>(); 
     Stack<Character> stack = new Stack<Character>(); 
     Character ch; 
     String digits=""; 
     String letters = ""; 


     for(int i=0; i<infix.length(); i++) 
     { 
      ch=infix.charAt(i); 
      if(ch == ' ') 
      { 
       //do nothing 
      } 

      if(Character.isDigit(ch)) 
      { 

       digits=""+ch; 
       if(i+1 >= infix.length() || !Character.isDigit(infix.charAt(i+1))) 
       { 
        digits=digits+""; 
       } 
       postfix.add(digits); 


      } 
      if(Character.isLetter(ch)) 
      { 
       letters=ch+""; 

       postfix.add(letters); 

      } 

      if(isOperator(ch)) 
      { 
       if(ch == ')') 
       { 

        if(!stack.isEmpty() && stack.peek() != '(') 
        { 
         postfix.add(""+stack.pop()); 
         if(!stack.isEmpty()) 
         { 
          stack.pop(); 
         } 
        } 
       } 

       else 
       { 

        if(!stack.isEmpty() && !lowerEqualPrec(ch, stack.peek())) 
        { 
         stack.push(ch); 
        } 

        else 
        { 
         while(!stack.isEmpty() && lowerEqualPrec(ch, stack.peek())) 
         { 
          char pop = stack.pop(); 
          if(ch!='(') 
          { 
           postfix.add(pop+""); 
          } 
         } 

         stack.push(ch); 
        } 
       } 
      } 
     } 
     while(!stack.isEmpty()&&stack.peek()!='(') 
     { 
      postfix.add(stack.pop()+""); 
     } 
     System.out.println(postfix); 
    } 

    public Iterator<String> iterator() 
    { 
     return new PostfixIterator(postfix) ; 
    } 

    public static void main(String[] args) 
    { 
     InfixToPostfix test = new InfixToPostfix("1002+304"); 
    } 

} 

Answer 1

Pour postfixConversion

public static String postfixConversion(String input) { 

     int i; 
     String postfix = ""; 

     Stack<Character> stack = new Stack<Character>(); 

     for (i = 0; i < input.length(); i++) { 
       while (input.charAt(i) == ' ') { 
         ++i; 
       } 

       if (Character.isDigit(input.charAt(i))) { 
           postfix += input.charAt(i); 

           //if (!Character.isDigit(input.charAt(i+1))) { 
             postfix += ' '; 
           //} 
       } 

       else if (precedenceLevel(input.charAt(i)) != 0) { 
         while ((!stack.isEmpty()) && (precedenceLevel(stack.peek()) >= precedenceLevel(input.charAt(i))) && (stack.peek() != '(')) { 
           postfix += stack.peek(); 
           postfix += ' '; 
           stack.pop(); 
         } 

         stack.push(input.charAt(i)); 
       } 

       else if (input.charAt(i) == '(') { 
         stack.push(input.charAt(i)); 
       } 

       else if (input.charAt(i) == ')') { 
         while (!stack.isEmpty() && stack.peek() != '(') { 
           postfix += stack.peek(); 
           stack.pop(); 
         } 

         stack.pop(); 
       } 
     } 

     while (!stack.isEmpty()) { 
       postfix += stack.peek(); 
       postfix += ' '; 
     } 

     return postfix; 

}