为什么这个 c# Palindrome 程序不起作用？

Question

using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;

namespace Palindrome
{
    class Program
    {
        static void Main(string[] args)
        {


            string filePath = @"C:\Users\Me\Desktop\Palindromes\palindromes.txt";
            //This gets the file we need

            var meStack = new Stack<string>();
            //this  creates the stack

            foreach (var item in File.ReadLines(filePath))
            {
                meStack.Push(item.ToUpper());
            }
            //for every item in the file, push onto the stack and make it upper case


            while (meStack.TryPop(out string Line))
            {
                reverseMe(Line);
            }
            //While every line in the stack is popped out, every line goes to the fucntion reverseMe






            static bool reverseMe(string Line)
            {
                return
                    Line == Line.Reverse();
            }
            //return true if line is the same as the line backwards or false if its not.


        }
    }

}

How do I get output? I have written comments to try and understand... but I am not getting a console output. I want the code to take in the file, put all the strings into a stack, and send every line in that stack to the reverseMe() function, which is a bool. The bool will see if the string is the same forward as it is backwards and if so it will return true or false. Basically my console is empty when I try to run this code.. What do I do?

Answer 1

There is a problem in the method reverseMe , The function Reverse gives you collection of char if applied on string , then you need to convert IEnumerable<char> to string by new string() or string.Concat() , like the following code:

static bool reverseMe(string Line)
{
    //deleting whitespaces, tabs
    Line = Regex.Replace(Line, @"\s+", "");

    return Line == new string(Line.Reverse().ToArray());
    //or
    //return Line == string.Concat(Line.Reverse());
    //or like Dmitry comment
    //return Line.SequenceEqual(Line.Reverse());
}

Calling reverseMe , and output result like : word is not palindrome

while (meStack.TryPop(out string Line))
{
    string isOrNotPalindrome = reverseMe(Line) ? string.Empty : "not";
    Console.WriteLine($"{Line} is {isOrNotPalindrome} palindrome");
}

Demo

bool isPalindrome1 = reverseMe("madam");
bool isPalindrome2 = reverseMe("nurses run");
bool isPalindrome3 = reverseMe("AaBbbBaAp");

Result

true
true
false

I hope this will help you fix the issue

Answer 2

Let's start from the problem; I assume that you want to scan all file's lines and print out if the line is a palindrom.

First, we need to implement IsPalindrom method:

private static bool IsPalindrom(string value) {
  if (null == value)
    return false; // or true, ot throw ArgumentNullException

  // We have to prepare the string: when testing for palindrom
  //  1. Let's ignore white spaces (' ', '\r', '\t' etc.)
  //  2. Let's ignore punctuation  (':', ',' etc.)
  //  3. Let's ignore cases        (i.e. 'M' == 'm') 
  // So "Madam, I'm Adam" will be a proper palindrom
  value = string.Concat(value
    .Where(c => !char.IsWhiteSpace(c))
    .Where(c => !char.IsPunctuation(c))
    .Select(c => char.ToUpperInvariant(c)));

  // Instead of Reversing we can just compare:
  // [0] and [Length - 1] then [1] and [Length - 2] etc.
  for (int i = 0; i < value.Length / 2; ++i)
    if (value[i] != value[value.Length - 1 - i])
      return false; // we have a counter example: value is NOT a palidrom

  // Value has been scanned, no counter examples are found
  return true;    
}

Time to write Main method:

static void Main(string[] args) {
  string filePath = @"C:\Users\Me\Desktop\Palindromes\palindromes.txt";

  var result = File
    .ReadLines(filePath)
    .Where(line => !string.IsNullOrWhiteSpace(line)) // let's skip empty lines
    .Select(line => $"{(IsPalindrom(line) ? "Palindrom" : "Not a palindrom")}: \"{line}\"");

  // Do not forget to print result on the Console:
  foreach (var record in result)   
    Console.WriteLine(record);

  // Pause to have a look at the outcome (wait for a key to be pressed)
  Console.ReadKey(); 
} 

Answer 3

嗯，从 reverseMe() 函数获得结果后，没有 Console.WriteLine() 来执行任何实际输出。