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  1. using System;
  2. using System.Text;
  3. using System.Collections.Generic;
  4. using System.Linq;
  5. using System.Collections;
  6.  
  7. public class InFixtoPostFix
  8. {
  9. 	public static void Main()
  10. 	{
  11. 		// your code goes here
  12.  
  13. 		string[] inputString = {"5","+","3","*","6","-","4","+","8"};
  14. 		string[] outputString;
  15. 		outputString=InFixtoPostFix.infixToPostFix(inputString);
  16. 		foreach(string token in outputString)
  17. 		{
  18. 			Console.WriteLine(token);
  19. 		}
  20. 	}
  21.  
  22. 	        public enum Precedence
  23.         {
  24.             Prod = 3,Sub = 2, Add = 1 
  25.         }
  26.  
  27.  
  28. 		/// <summary>
  29.         /// converts an infix expression to postfix expression
  30.         /// *,+,- in the order of precedence
  31.         /// </summary>
  32.         /// <param name="inputExpression"></param>
  33.         /// <returns></returns>
  34.         public static string[] infixToPostFix(string[] inputExpression)
  35.         {
  36.             Stack<string> opStack;
  37.             string[] output;
  38.             int i, j;
  39.  
  40.             if (inputExpression == null) return null;
  41.             opStack = new Stack<string>();
  42.             output = new string[inputExpression.Length];
  43.  
  44.             i=0;
  45.             j = 0;
  46.  
  47.             while (i < inputExpression.Length)
  48.             {
  49.             	// check if token is number
  50.                 if (IsNumber(inputExpression[i]))
  51.                 {
  52.                     output[j++] = inputExpression[i++];
  53.                 }
  54.                 // check if token is operator
  55.                 else if(IsOperator(inputExpression[i]))
  56.                 {
  57.                     if(opStack.Count() != 0)
  58.                     {
  59.                     while (getPrecedence(opStack.Peek().ToString()) >= getPrecedence(inputExpression[i]))
  60.                     {
  61.                         output[j++] = opStack.Pop().ToString();
  62.                         if (opStack.Count() == 0)  break;
  63.                     }
  64.  
  65.                     opStack.Push(inputExpression[i++]);
  66.                     }
  67.                     else
  68.                     opStack.Push(inputExpression[i++]);
  69.                 }
  70.                 // non-operator return null string
  71.                 else 
  72.                 {
  73.                 	return null;
  74.                 }
  75.             }
  76.             while (opStack.Count() != 0)
  77.             {
  78.                 output[j++] = opStack.Pop().ToString();
  79.             }
  80.  
  81.             return output;
  82.         }
  83.  
  84.         public static int  getPrecedence(string inputString)
  85.         {
  86.             switch (inputString)
  87.             {
  88.                 case "*":
  89.                     return (int)Precedence.Prod; 
  90.                 case "-":
  91.                     return (int)Precedence.Sub;
  92.                 case "+":
  93.                     return (int)Precedence.Add;
  94.             }
  95.  
  96.             return -1;
  97.         }
  98.  
  99.         public static bool IsNumber(string inputString)
  100.         {
  101.             try
  102.             {
  103.                 Convert.ToInt32(inputString);
  104.                 return true;
  105.             }
  106.             catch (System.FormatException ex)
  107.             {
  108.                 Console.WriteLine("Not a Number");
  109.                 return false;
  110.             }
  111.         }
  112.  
  113.         public static bool IsOperator(string inputstring)
  114.         {
  115.         	switch(inputstring)
  116.         	{
  117.         		case "*": return true;
  118.         		case "+": return true;
  119.         		case "-": return true;
  120.         	}
  121.         	return false;
  122.         }
  123. }
Success #stdin #stdout 0.03s 33992KB
comments (?)
stdin
copy 
Standard input is empty
stdout
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Not a Number
Not a Number
Not a Number
Not a Number
5
3
6
*
4
-
+
8
+
https://ideone.com/rBz6fW
language:
C# (gmcs 5.20.1)
created:
10 years ago
visibility:
public

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