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refactor: redesign LetterCombinationsOfPhoneNumber (#5221)

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* Refactor

* fix clang

* fix clang

* fix clang tests

* fix pattern

* add test case null

* Update src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* Update src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* Update src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* Update src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* Update src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* Update src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* Update src/test/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumberTest.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* rename MAP_OF_CHARS to KEYPAD

* fix clang

* remove main

* add tests

* feat: throw for wrong inputs

* change keypad to list

* Update src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* Update src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* Update src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>

* fix with number 1 (empty value), and add tests

* style: avoid concatenation while populating `KEYPAD`

* change to assertEquals

---------

Co-authored-by: Samuel Facchinello <samuel.facchinello@piksel.com>
Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>
This commit is contained in:
Samuel Facchinello
2024-06-13 19:40:12 +02:00
committed by GitHub
parent 31db1af345
commit 51fcc66345
2 changed files with 71 additions and 67 deletions
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src/main/java/com/thealgorithms/strings/LetterCombinationsOfPhoneNumber.java
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@ -5,49 +5,61 @@ import java.util.Collections;
import java.util.List;
public final class LetterCombinationsOfPhoneNumber {
private static final char EMPTY = '\0';
// Mapping of numbers to corresponding letters on a phone keypad
private static final String[] KEYPAD = new String[] {" ", String.valueOf(EMPTY), "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
private LetterCombinationsOfPhoneNumber() {
}
static Character[][] numberToCharMap;
/**
* Generates a list of all possible letter combinations that the provided
* array of numbers could represent on a phone keypad.
*
* @param numbers an array of integers representing the phone numbers
* @return a list of possible letter combinations
*/
public static List<String> getCombinations(int[] numbers) {
if (numbers == null) {
return List.of("");
}
return generateCombinations(numbers, 0, new StringBuilder());
}
protected static List<String> printWords(int[] numbers, int len, int numIndex, String s) {
if (len == numIndex) {
return new ArrayList<>(Collections.singleton(s));
/**
* Recursive method to generate combinations of letters from the phone keypad.
*
* @param numbers the input array of phone numbers
* @param index the current index in the numbers array being processed
* @param current a StringBuilder holding the current combination of letters
* @return a list of letter combinations formed from the given numbers
*/
private static List<String> generateCombinations(int[] numbers, int index, StringBuilder current) {
// Base case: if we've processed all numbers, return the current combination
if (index == numbers.length) {
return new ArrayList<>(Collections.singletonList(current.toString()));
}
List<String> stringList = new ArrayList<>();
for (int i = 0; i < numberToCharMap[numbers[numIndex]].length; i++) {
String sCopy = String.copyValueOf(s.toCharArray());
sCopy = sCopy.concat(numberToCharMap[numbers[numIndex]][i].toString());
stringList.addAll(printWords(numbers, len, numIndex + 1, sCopy));
final var number = numbers[index];
if (number < 0 || number > 9) {
throw new IllegalArgumentException("Input numbers must in the range [0, 9]");
}
return stringList;
}
private static void printWords(int[] numbers) {
generateNumberToCharMap();
List<String> stringList = printWords(numbers, numbers.length, 0, "");
stringList.stream().forEach(System.out::println);
}
List<String> combinations = new ArrayList<>();
protected static void generateNumberToCharMap() {
numberToCharMap = new Character[10][5];
numberToCharMap[0] = new Character[] {'\0'};
numberToCharMap[1] = new Character[] {'\0'};
numberToCharMap[2] = new Character[] {'a', 'b', 'c'};
numberToCharMap[3] = new Character[] {'d', 'e', 'f'};
numberToCharMap[4] = new Character[] {'g', 'h', 'i'};
numberToCharMap[5] = new Character[] {'j', 'k', 'l'};
numberToCharMap[6] = new Character[] {'m', 'n', 'o'};
numberToCharMap[7] = new Character[] {'p', 'q', 'r', 's'};
numberToCharMap[8] = new Character[] {'t', 'u', 'v'};
numberToCharMap[9] = new Character[] {'w', 'x', 'y', 'z'};
}
// Iterate over each letter and recurse to generate further combinations
for (char letter : KEYPAD[number].toCharArray()) {
if (letter != EMPTY) {
current.append(letter);
}
combinations.addAll(generateCombinations(numbers, index + 1, current));
if (letter != EMPTY) {
current.deleteCharAt(current.length() - 1); // Backtrack by removing the last appended letter
}
}
// Driver code
public static void main(String[] args) {
int[] number = {2, 3, 4};
printWords(number);
return combinations;
}
}