Implementing Basic Autocomplete

Implementing a basic autocomplete feature using std::string is a great way to practice string manipulation and searching. Let's create a simple autocomplete function that suggests words from a predefined list based on a user's input prefix.

Here's a step-by-step implementation:

1. Create a list of words (our dictionary) using std::vector<std::string>.
2. Write a function that takes a prefix and the dictionary as input.
3. Use std::string::starts_with() to find matches (C++20 feature).
4. Return a list of matching words.

Here's the code implementation:

1#include <iostream>
2#include <string>
3#include <vector>
4#include <algorithm>
5
6std::vector<std::string> autocomplete(
7    const std::string& prefix,
8    const std::vector<std::string>& dictionary) {
9  std::vector<std::string> suggestions;
10
11  for (const auto& word : dictionary) {
12    if (word.starts_with(prefix)) {  
13      suggestions.push_back(word);
14    }
15  }
16
17  return suggestions;
18}
19
20int main() {
21  std::vector<std::string> dictionary{
22    "cat", "dog", "elephant",
23    "lion", "tiger", "leopard"
24  };
25
26  std::string prefix;
27  std::cout << "Enter a prefix: ";
28  std::cin >> prefix;
29
30  auto suggestions =
31    autocomplete(prefix, dictionary);
32
33  std::cout << "Suggestions:\n";
34  for (const auto& suggestion : suggestions) {
35    std::cout << suggestion << '\n';
36  }
37}

1Enter a prefix: l
2Suggestions:
3lion
4leopard

Let's break down the autocomplete() function:

1. It takes a prefix and a dictionary as input.
2. It creates an empty vector suggestions to store matching words.
3. It iterates through each word in the dictionary.
4. If a word starts with the given prefix (using starts_with()), it's added to suggestions.
5. Finally, it returns the list of suggestions.

In main(), we create a sample dictionary, get a prefix from the user, call autocomplete(), and print the suggestions.

This basic implementation can be enhanced in several ways:

• Sort the suggestions alphabetically using std::sort().
• Limit the number of suggestions returned.
• Implement case-insensitive matching.
• Use more efficient data structures like tries for larger dictionaries.

Remember, std::string::starts_with() is a C++20 feature. If you're using an older C++ version, you can replace it with:

1if (word.substr(0, prefix.length()) == prefix) {
2  suggestions.push_back(word);
3}

This autocomplete feature demonstrates the power and flexibility of std::string in C++, showcasing methods like starts_with() and how they can be used in practical applications.