c# collections questions

Question

can anybody help me to find out the following questions
1) input a sentance and print the frequency of words repeating in the sentance. use arraylist or hash table
2) create a linked list . add new elements and delete existing elements and traverse through the list
3)write a prgm that accept a postfix expression nd determines its value.
input specification:
the input to the prm will consist os a well formed postfix expresion terminated by a newline charector ('
'). the expression will consist of operands and operators seperated by a single sapace . this possible operators are
+ Adddition
- subtratoin
* multiplication
/ integer division
% remainder
^ exponentiation
operants will be positive integers
input will not be such tht it will cause an overflow or underflow in an integer variable
output spec
output should be the value of the expression follwed by a newline charector
example
input
10 20+
output
30
input
9 8+3 5 - /
output
-8
input
7 3 2 ^ %
output
8

Vulpes · Accepted Answer

/* problem 1 */
using System; using System.Collections;
class Program {    static void Main()    {        Hashtable ht = new Hashtable();        Console.WriteLine("Please enter a sentence
");        string sentence = Console.ReadLine();          // treat hyphen or apostrophe as being part of word          char[] separators = " .,:;!?(){}[]<>@"".ToCharArray();               string[] words = sentence.Split(separators, StringSplitOptions.RemoveEmptyEntries);
for(int i = 0; i        {           string word = words[i].ToLower(); // ignore capitalization             if(ht.ContainsKey(word))           {               ht[word] = (int)ht[word] + 1;           }           else           {               ht.Add(word, 1);           }        }           Console.WriteLine("
The frequency of words in the sentence is as follows
");               foreach(string key in ht.Keys)        {            Console.WriteLine(" {0, -20} {1, 2}", key, ht[key]);        }          Console.WriteLine("
{0, -21} {1,2}", "Total", words.Length);
Console.ReadKey();    } }
/* problem 2 */
using System; using System.Collections.Generic;
class Program {    static void Main()    {       LinkedList carMakes = new LinkedList ();       carMakes.AddLast("Volkswagen");       carMakes.AddLast("Ford");       carMakes.AddLast("Kia");       carMakes.AddLast("Vauxhall");       carMakes.AddFirst("Jaguar");       carMakes.Remove("Audi");       carMakes.Remove("Kia");       foreach(string carMake in carMakes) Console.WriteLine(carMake);       Console.ReadKey();    } }
/* problem 3 */
using System; using System.Collections.Generic;
class Program {    static void Main()    {       Stack s = new Stack ();       Console.Write("Enter a postfix expression : ");       string expr = Console.ReadLine().Trim();       string[] tokens = expr.Split(' ');       foreach(string token in tokens)       {          int num;          bool isValid = int.TryParse(token, out num);          if (isValid)          {             s.Push(num);          }          else          {             int num1 = s.Pop();             int num2 = s.Pop();
switch(token)             {                case "+" :                  s.Push(num1 + num2);                  break;
case "-" :                  s.Push(num2 - num1);                  break;                                  case "*" :                  s.Push(num1 * num2);                  break;                  case "/" :                  s.Push(num2 / num1);                  break;
case "%" :                  s.Push(num2 % num1);                  break;
case "^" :                  s.Push((int)Math.Pow(num2, num1));                  break;             }          }       }
Console.WriteLine("The result is {0}", s.Pop());       Console.ReadKey();    } }
Note that last expression 7 3 2 ^ % has a value of 7 not 8. That's because:
3 ^ 2 = 9 and 7 % 9 = 7

Sinu Joseph · Answer

Thank u  Vulpes ...