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refactor: Enhance docs, add more tests in ArrayCombination (#5841)

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This commit is contained in:
Hardik Pawar
2024-10-15 14:29:16 +05:30
committed by GitHub
parent adf21ab0c8
commit 32bf532133
2 changed files with 26 additions and 10 deletions
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28
src/main/java/com/thealgorithms/backtracking/ArrayCombination.java
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@ -4,22 +4,24 @@ import java.util.ArrayList;
import java.util.List;
/**
* Finds all combinations of 0...n-1 of length k
* This class provides methods to find all combinations of integers from 0 to n-1
* of a specified length k using backtracking.
*/
public final class ArrayCombination {
private ArrayCombination() {
}
/**
* Finds all combinations of length k of 0..n-1 using backtracking.
* Generates all possible combinations of length k from the integers 0 to n-1.
*
* @param n Number of the elements.
* @param k Length of the combination.
* @return A list of all combinations of length k.
* @param n The total number of elements (0 to n-1).
* @param k The desired length of each combination.
* @return A list containing all combinations of length k.
* @throws IllegalArgumentException if n or k are negative, or if k is greater than n.
*/
public static List<List<Integer>> combination(int n, int k) {
if (n < 0 || k < 0 || k > n) {
throw new IllegalArgumentException("Wrong input.");
throw new IllegalArgumentException("Invalid input: n must be non-negative, k must be non-negative and less than or equal to n.");
}
List<List<Integer>> combinations = new ArrayList<>();
@ -27,9 +29,19 @@ public final class ArrayCombination {
return combinations;
}
/**
* A helper method that uses backtracking to find combinations.
*
* @param combinations The list to store all valid combinations found.
* @param current The current combination being built.
* @param start The starting index for the current recursion.
* @param n The total number of elements (0 to n-1).
* @param k The desired length of each combination.
*/
private static void combine(List<List<Integer>> combinations, List<Integer> current, int start, int n, int k) {
if (current.size() == k) { // Base case: combination found
combinations.add(new ArrayList<>(current)); // Copy to avoid modification
// Base case: combination found
if (current.size() == k) {
combinations.add(new ArrayList<>(current));
return;
}