Implement Parentheses Generator (#5096)

* chore: add `ParenthesesGenerator` to `DIRECTORY.md`

* feat: implement Parentheses Generator

* ref: change `ParenthesesGenerator`s method to `static`

* ref: use parametrized tests

* ref: handling exception when `n < 0`

* chore: update docstrings

* ref: make `ParenthesesGenerator` to be a proper utility

* chore(docs): add private constructor docstring

* ref(tests): move bad name suggestions

* style: remove reduntant comments

---------

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>
This commit is contained in:
SOZEL
2024-04-05 23:41:27 +07:00
committed by GitHub
parent 22310defcd
commit c53f178308
3 changed files with 84 additions and 0 deletions

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@ -0,0 +1,50 @@
package com.thealgorithms.backtracking;
import java.util.ArrayList;
import java.util.List;
/**
* This class generates all valid combinations of parentheses for a given number of pairs using backtracking.
*/
public final class ParenthesesGenerator {
private ParenthesesGenerator() {
}
/**
* Generates all valid combinations of parentheses for a given number of pairs.
*
* @param n The number of pairs of parentheses.
* @return A list of strings representing valid combinations of parentheses.
* @throws IllegalArgumentException if n is less than 0.
*/
public static List<String> generateParentheses(final int n) {
if (n < 0) {
throw new IllegalArgumentException("The number of pairs of parentheses cannot be nagative");
}
List<String> result = new ArrayList<>();
generateParenthesesHelper(result, "", 0, 0, n);
return result;
}
/**
* Helper function for generating all valid combinations of parentheses recursively.
*
* @param result The list to store valid combinations.
* @param current The current combination being formed.
* @param open The number of open parentheses.
* @param close The number of closed parentheses.
* @param n The total number of pairs of parentheses.
*/
private static void generateParenthesesHelper(List<String> result, final String current, final int open, final int close, final int n) {
if (current.length() == n * 2) {
result.add(current);
return;
}
if (open < n) {
generateParenthesesHelper(result, current + "(", open + 1, close, n);
}
if (close < open) {
generateParenthesesHelper(result, current + ")", open, close + 1, n);
}
}
}