Problem Description
Given a list of words and a word to search for, the task is to check whether the search word is included in the word list. This problem can
be solved using a dictionary data structure. This can be easily implemented in C# using the Dictionary class.
Algorithm Problem
Problem
Given a list of words words, write the following checkWords method.
The checkWords method takes a list of strings and a string as parameters, and it should return true if the
string is in the list, and false if it is not.
Example
Input: words = ["apple", "banana", "cherry"], searchWord = "banana"
Output: true
Solution
One of the most efficient methods to solve this problem is by using a hash table. By using a hash table to store the list of words
beforehand, we can find words with O(1) time complexity during searches. Utilizing C#’s Dictionary class allows
us to implement this, so we will solve the problem using the following steps.
Step 1: Convert the Word List to a Dictionary
First, we will convert the given word list into a Dictionary. Each word will be used as a key and the value will be
an unnecessary empty string.
// C# code
using System;
using System.Collections.Generic;
public class DictionarySearch
{
private Dictionary wordDictionary;
public DictionarySearch(List words)
{
wordDictionary = new Dictionary();
foreach (var word in words)
{
wordDictionary[word] = true; // Value is not needed, set to true
}
}
}
Step 2: Write the Word Search Method
Now, we will write the checkWords method. This method will check whether the word being searched exists in the dictionary.
public bool CheckWords(string searchWord)
{
return wordDictionary.ContainsKey(searchWord);
}
Step 3: Implement the Final Class and Method
We will combine the above steps to complete the class as a final solution.
using System;
using System.Collections.Generic;
public class DictionarySearch
{
private Dictionary wordDictionary;
public DictionarySearch(List words)
{
wordDictionary = new Dictionary();
foreach (var word in words)
{
wordDictionary[word] = true;
}
}
public bool CheckWords(string searchWord)
{
return wordDictionary.ContainsKey(searchWord);
}
}
class Program
{
static void Main(string[] args)
{
List words = new List { "apple", "banana", "cherry" };
DictionarySearch dictionarySearch = new DictionarySearch(words);
Console.WriteLine(dictionarySearch.CheckWords("banana")); // Output: true
Console.WriteLine(dictionarySearch.CheckWords("grape")); // Output: false
}
}
Complexity Analysis
– Time complexity: O(1) – Using a hash table to store and search for words is optimally performed in O(1) time.
– Space complexity: O(n) – Proportional to the size n of the given word list.
Key Points
– Using the Dictionary class is key to solving the problem. It ensures fast search speeds.
– In string comparisons, the results may differ based on case sensitivity, so caution is needed.
– After running the overall code, it is necessary to validate it through various test cases.
Conclusion
In this tutorial, we explained how to solve the dictionary search problem using C#. We demonstrated that a data structure approach
utilizing a hash table can efficiently satisfy the problem’s given conditions. The use of such data structures is frequently encountered
in actual coding tests, so practicing in advance is important.