Reverse A String And Find Word In String

In this blog, you will learn how to reverse a string and find a word in string using C#.

I will demonstrate how to reverse a string in a simple way and how to find a specfic word in the given string using C#. Here is the code sample that shows you  how to reverse a string in C# and find the desired word in a given string.

 

Reverse a string in simple steps using C#.

public string ReverseString(string input)
{
    if (string.IsNullOrEmpty(input))
    {
        throw new ArgumentNullException();
    }

    var output = input.Reverse();
    return new string(output.ToArray());
}

Find a word in given string. We assume the separator of word is space (' ');

/// Example 1: GetWordFromText("one two three", 2) should return "two"
/// Example 2: GetWordFromText("one;two three", 2) should return "three"
/// Example 3: GetWordFromText("one", 1) should return "one"
/// When input parameter wordNumberToFind is less than 1, method should throw
/// ArgumentOutOfRangeException. When input text does not have enough words
/// (GetWordFromText("one", 2)), method should throw ArgumentException.
/// When input is null method should throw `ArgumentNullException`.
/// Method should ignore all spaces in the beginning and in the end of input text.
/// </returns>
public string GetWordFromText(string input, int wordNumberToFind)
{

    // TODO: Implement logic HERE
    if (wordNumberToFind < 1)
    {
        throw new ArgumentOutOfRangeException();
    }

    if (string.IsNullOrWhiteSpace(input))
    {
        throw new ArgumentNullException();
    }

    var words = input.Split(' ');

    if (wordNumberToFind > words.Length)
    {
        throw new ArgumentException();
    }

    while (string.IsNullOrWhiteSpace(words[wordNumberToFind - 1]))
    {
        wordNumberToFind++;
    }

    return words[wordNumberToFind - 1];
}

Let's have some unit tests to verify the above code.

namespace TaskLib.Tests
{
    using System;

    using FluentAssertions;
    using NUnit.Framework;

    [TestFixture]
    public class StringTests
    {
        [Test]
        public void When_WordToFindIsNotInTheInput_Then_ArgumentExceptionIsThrown()
        {
            // Arrange
            var tested = new StringHelpers();

            // Act
            Assert.Throws<ArgumentException>(() => { var word = tested.GetWordFromText("two words", 3); });
        }

        [Test]
        public void When_InputTextContainsFewWords_Then_ProperOneIsReturned()
        {
            // Arrange
            var tested = new StringHelpers();

            // Act
            var word = tested.GetWordFromText("one;two  three", 2);

            // Assert
            word.Should().Be("three");
        }

        [Test]
        public void When_InputTextIsSymmetrical_Then_ItIsReturned()
        {
            // Arrange
            var tested = new StringHelpers();

            // Act
            var reversed = tested.Reverse("evil live");

            // Assert
            reversed.Should().Be("evil live");
        }

        [Test]
        public void When_InputTextIsPassed_Then_ItIsReversed()
        {
            // Arrange
            var tested = new StringHelpers();

            // Act
            var reversed = tested.Reverse("abcd efgh");

            // Assert
            reversed.Should().Be("hgfe dcba");
        }
    }
}

Thanks. I hope you liked this simple approach of reversing a string and finding a word in the string.