22. Generate Parentheses

```Solution.c /** * Note: The returned array must be malloced, assume caller calls free(). */ void backtrack(char **result, char *current, int open, int close, int n, int *count) {	if (open == n && close == n) {	current[open + close] = '\0';	result[*count] = (char *)malloc((2 * n + 1) * sizeof(char));	strcpy(result[*count], current);	(*count)++;	return;	}	if (open < n) {	current[open + close] = '(';	backtrack(result, current, open + 1, close, n, count);	}	if (close < open) {	current[open + close] = ')';	backtrack(result, current, open, close + 1, n, count);	} } char** generateParenthesis(int n, int* returnSize) {	int maxSize = 1;	for (int i = 0; i < n; ++i) {	maxSize = maxSize * 2 * (2 * i + 1) / (i + 2);	}	char **result = (char **)malloc(maxSize * sizeof(char *));	char *current = (char *)malloc((2 * n + 1) * sizeof(char));	current[2 * n] = '\0';	int count = 0;	backtrack(result, current, 0, 0, n, &count);	free(current);	*returnSize = count;	return result; } ``` ```Solution.cpp class Solution { public: vector<string> generateParenthesis(int n) { vector<string> result; function<void(string, int, int)> backtrack = [&](string curr, int open, int close) { if (curr.size() == n * 2) { result.push_back(curr); return; } if (open < n) backtrack(curr + '(', open + 1, close); if (close < open) backtrack(curr + ')', open, close + 1); }; backtrack("", 0, 0); return result; } }; ``` ```Solution.cs public class Solution { public IList<string> GenerateParenthesis(int n) { IList<string> result = new List<string>(); char[] current = new char[2 * n]; backtrack(result, current, 0, 0, n); return result; } private void backtrack(IList<string> result, char[] current, int open, int close, int n) { if (open == n && close == n) { result.Add(new string(current)); return; } if (open < n) { current[open + close] = '('; backtrack(result, current, open + 1, close, n); } if (close < open) { current[open + close] = ')'; backtrack(result, current, open, close + 1, n); } } } ``` ```Solution.dart class Solution { List<String> generateParenthesis(int n) { List<String> result = []; void backtrack(String current, int open, int close) { if (current.length == n * 2) { result.add(current); return; } if (open < n) { backtrack(current + '(', open + 1, close); } if (close < open) { backtrack(current + ')', open, close + 1); } } backtrack('', 0, 0); return result; } } ``` ```Solution.erl -spec generate_parenthesis(N :: integer()) -> [unicode:unicode_binary()]. generate_parenthesis(N) -> generate(N, N, <<>>). generate(0, 0, Acc) -> [Acc]; generate(Open, Close, Acc) when Open > 0, Open =< Close -> generate(Open - 1, Close, <<Acc/binary, "(">>) ++ (if Close > Open -> generate(Open, Close - 1, <<Acc/binary, ")">>); true -> [] end); generate(Open, Close, Acc) when Close > Open -> generate(Open, Close - 1, <<Acc/binary, ")">>); generate(_, _, _) -> []. ``` ```Solution.ex defmodule Solution do @SPEC generate_parenthesis(n :: integer) :: [String.t] def generate_parenthesis(n) do generate([], "", 0, 0, n) end defp generate(acc, curr, open, close, n) do if String.length(curr) == n * 2 do [curr | acc] else acc = if open < n do generate(acc, curr <> "(", open + 1, close, n) else acc end if close < open do generate(acc, curr <> ")", open, close + 1, n) else acc end end end end ``` ```Solution.go func generateParenthesis(n int) []string {	var res []string	var backtrack func(s string, left, right int)	backtrack = func(s string, left, right int) {	if len(s) == 2*n {	res = append(res, s)	return	}	if left < n {	backtrack(s+"(", left+1, right)	}	if right < left {	backtrack(s+")", left, right+1)	}	}	backtrack("", 0, 0)	return res } ``` ```Solution.java class Solution { public List<String> generateParenthesis(int n) { List<String> result = new ArrayList<>(); backtrack(result, "", 0, 0, n); return result; } private void backtrack(List<String> result, String current, int open, int close, int max) { if (current.length() == max * 2) { result.add(current); return; } if (open < max) { backtrack(result, current + "(", open + 1, close, max); } if (close < open) { backtrack(result, current + ")", open, close + 1, max); } } } ``` ```Solution.js /** * @param {number} n * @return {string[]} */ var generateParenthesis = function(n) { var result = []; var backtrack = function(current, open, close) { if (current.length === n * 2) { result.push(current); return; } if (open < n) { backtrack(current + '(', open + 1, close); } if (close < open) { backtrack(current + ')', open, close + 1); } }; backtrack('', 0, 0); return result; }; ``` ```Solution.kt class Solution { fun generateParenthesis(n: Int): List<String> { val result = mutableListOf<String>() fun backtrack(current: String, open: Int, close: Int) { if (current.length == n * 2) { result.add(current) return } if (open < n) { backtrack(current + "(", open + 1, close) } if (close < open) { backtrack(current + ")", open, close + 1) } } backtrack("", 0, 0) return result } } ``` ```Solution.php class Solution { /** * @param Integer $n * @return String[] */ function generateParenthesis($n) { $result = []; $this->backtrack($result, "", 0, 0, $n); return $result; } private function backtrack(&$result, $current, $open, $close, $max) { if (strlen($current) == $max * 2) { $result[] = $current; return; } if ($open < $max) { $this->backtrack($result, $current . "(", $open + 1, $close, $max); } if ($close < $open) { $this->backtrack($result, $current . ")", $open, $close + 1, $max); } } } ``` ```Solution.py class Solution: def generateParenthesis(self, n: int) -> List[str]: result = [] self.backtrack(result, "", 0, 0, n) return result def backtrack(self, result, current, open, close, max): if len(current) == max * 2: result.append(current) return if open < max: self.backtrack(result, current + "(", open + 1, close, max) if close < open: self.backtrack(result, current + ")", open, close + 1, max) ``` ```Solution.rb # @param {Integer} n # @return {String[]} def generate_parenthesis(n) result = [] backtrack(result, "", 0, 0, n) return result end def backtrack(result, current, open, close, max) if current.length == max * 2 result << current return end if open < max backtrack(result, current + "(", open + 1, close, max) end if close < open backtrack(result, current + ")", open, close + 1, max) end end ``` ```Solution.rkt (define/contract (generate-parenthesis n) (-> exact-integer? (listof string?)) (define (loop left right s) (cond [(and (= left 0) (= right 0)) (list s)] [else (append (if (> left 0) (loop (- left 1) right (string-append s "(")) '()) (if (> right left) (loop left (- right 1) (string-append s ")")) '()))])) (loop n n "") ) ``` ```Solution.rs impl Solution { pub fn generate_parenthesis(n: i32) -> Vec<String> { let mut result = Vec::new(); Self::backtrack(&mut result, String::new(), 0, 0, n); result } fn backtrack(result: &mut Vec<String>, current: String, open: i32, close: i32, max: i32) { if current.len() == (max * 2) as usize { result.push(current); return; } if open < max { Self::backtrack(result, format!("{}(", current), open + 1, close, max); } if close < open { Self::backtrack(result, format!("{}{}", current, ")"), open, close + 1, max); } } } ``` ```Solution.scala object Solution { def generateParenthesis(n: Int): List[String] = { def backtrack(s: String, left: Int, right: Int): List[String] = { if (s.length == n * 2) List(s) else { val addLeft = if (left < n) backtrack(s + "(", left + 1, right) else Nil val addRight = if (right < left) backtrack(s + ")", left, right + 1) else Nil addLeft ++ addRight } } backtrack("", 0, 0) } } ``` ```Solution.swift class Solution { func generateParenthesis(_ n: Int) -> [String] { var result = [String]() backtrack(&result, "", 0, 0, n) return result } private func backtrack(_ result: inout [String], _ current: String, _ open: Int, _ close: Int, _ max: Int) { if current.count == max * 2 { result.append(current) return } if open < max { backtrack(&result, current + "(", open + 1, close, max) } if close < open { backtrack(&result, current + ")", open, close + 1, max) } } } ``` ```Solution.ts function generateParenthesis(n: number): string[] { const res: string[] = []; if (n === 0) return res; function generate(openN: number, closeN: number, path: string) { if (path.length === n * 2) { res.push(path); return; } if (openN < n) { generate(openN + 1, closeN, path + "("); } if (closeN < openN) { generate(openN, closeN + 1, path + ")"); } } generate(0, 0, ""); return res; }; ```

Author: nendroids

sol/solution/0001-0100/0022/README.md

@@ -0,0 +1,19 @@
+# [**22. Generate Parentheses**](https://leetcode.com/problems/generate-parentheses/description/)
+
+Given `n` pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
+
+#### **Example 1:**
+
+```md
+Input: n = 3
+Output: ["((()))","(()())","(())()","()(())","()()()"]
+```
+
+#### **Example 2:**
+```md
+Input: n = 1
+Output: ["()"]
+```
+
+#### **Constraints:**
+> - `1 <= n <= 8`

sol/solution/0001-0100/0022/Solution.c

@@ -0,0 +1,34 @@
+/**
+ * Note: The returned array must be malloced, assume caller calls free().
+ */
+void backtrack(char **result, char *current, int open, int close, int n, int *count) {
+if (open == n && close == n) {
+current[open + close] = '\0';
+result[*count] = (char *)malloc((2 * n + 1) * sizeof(char));
+strcpy(result[*count], current);
+(*count)++;
+return;
+}
+if (open < n) {
+current[open + close] = '(';
+backtrack(result, current, open + 1, close, n, count);
+}
+if (close < open) {
+current[open + close] = ')';
+backtrack(result, current, open, close + 1, n, count);
+}
+}
+char** generateParenthesis(int n, int* returnSize) {
+int maxSize = 1;
+for (int i = 0; i < n; ++i) {
+maxSize = maxSize * 2 * (2 * i + 1) / (i + 2);
+}
+char **result = (char **)malloc(maxSize * sizeof(char *));
+char *current = (char *)malloc((2 * n + 1) * sizeof(char));
+current[2 * n] = '\0';
+int count = 0;
+backtrack(result, current, 0, 0, n, &count);
+free(current);
+*returnSize = count;
+return result;
+}

sol/solution/0001-0100/0022/Solution.cpp

@@ -0,0 +1,18 @@
+class Solution {
+public:
+ vector<string> generateParenthesis(int n) {
+ vector<string> result;
+ function<void(string, int, int)> backtrack = [&](string curr, int open, int close) {
+ if (curr.size() == n * 2) {
+ result.push_back(curr);
+ return;
+ }
+ if (open < n)
+ backtrack(curr + '(', open + 1, close);
+ if (close < open)
+ backtrack(curr + ')', open, close + 1);
+ };
+ backtrack("", 0, 0);
+ return result;
+ }
+};

sol/solution/0001-0100/0022/Solution.cs

@@ -0,0 +1,22 @@
+public class Solution {
+ public IList<string> GenerateParenthesis(int n) {
+ IList<string> result = new List<string>();
+ char[] current = new char[2 * n];
+ backtrack(result, current, 0, 0, n);
+ return result;
+ }
+ private void backtrack(IList<string> result, char[] current, int open, int close, int n) {
+ if (open == n && close == n) {
+ result.Add(new string(current));
+ return;
+ }
+ if (open < n) {
+ current[open + close] = '(';
+ backtrack(result, current, open + 1, close, n);
+ }
+ if (close < open) {
+ current[open + close] = ')';
+ backtrack(result, current, open, close + 1, n);
+ }
+ }
+}

sol/solution/0001-0100/0022/Solution.dart

@@ -0,0 +1,19 @@
+class Solution {
+ List<String> generateParenthesis(int n) {
+ List<String> result = [];
+ void backtrack(String current, int open, int close) {
+ if (current.length == n * 2) {
+ result.add(current);
+ return;
+ }
+ if (open < n) {
+ backtrack(current + '(', open + 1, close);
+ }
+ if (close < open) {
+ backtrack(current + ')', open, close + 1);
+ }
+ }
+ backtrack('', 0, 0);
+ return result;
+ }
+}

sol/solution/0001-0100/0022/Solution.erl

@@ -0,0 +1,12 @@
+-spec generate_parenthesis(N :: integer()) -> [unicode:unicode_binary()].
+generate_parenthesis(N) ->
+ generate(N, N, <<>>).
+generate(0, 0, Acc) ->
+ [Acc];
+generate(Open, Close, Acc) when Open > 0, Open =< Close ->
+ generate(Open - 1, Close, <<Acc/binary, "(">>) ++
+ (if Close > Open -> generate(Open, Close - 1, <<Acc/binary, ")">>); true -> [] end);
+generate(Open, Close, Acc) when Close > Open ->
+ generate(Open, Close - 1, <<Acc/binary, ")">>);
+generate(_, _, _) ->
+ [].

sol/solution/0001-0100/0022/Solution.ex

@@ -0,0 +1,23 @@
+defmodule Solution do
+ @spec generate_parenthesis(n :: integer) :: [String.t]
+ def generate_parenthesis(n) do
+ generate([], "", 0, 0, n)
+ end
+ defp generate(acc, curr, open, close, n) do
+ if String.length(curr) == n * 2 do
+ [curr | acc]
+ else
+ acc =
+ if open < n do
+ generate(acc, curr <> "(", open + 1, close, n)
+ else
+ acc
+ end
+ if close < open do
+ generate(acc, curr <> ")", open, close + 1, n)
+ else
+ acc
+ end
+ end
+ end
+end

sol/solution/0001-0100/0022/Solution.go

@@ -0,0 +1,18 @@
+func generateParenthesis(n int) []string {
+var res []string
+var backtrack func(s string, left, right int)
+backtrack = func(s string, left, right int) {
+if len(s) == 2*n {
+res = append(res, s)
+return
+}
+if left < n {
+backtrack(s+"(", left+1, right)
+}
+if right < left {
+backtrack(s+")", left, right+1)
+}
+}
+backtrack("", 0, 0)
+return res
+}

sol/solution/0001-0100/0022/Solution.java

@@ -0,0 +1,19 @@
+class Solution {
+ public List<String> generateParenthesis(int n) {
+ List<String> result = new ArrayList<>();
+ backtrack(result, "", 0, 0, n);
+ return result;
+ }
+ private void backtrack(List<String> result, String current, int open, int close, int max) {
+ if (current.length() == max * 2) {
+ result.add(current);
+ return;
+ }
+ if (open < max) {
+ backtrack(result, current + "(", open + 1, close, max);
+ }
+ if (close < open) {
+ backtrack(result, current + ")", open, close + 1, max);
+ }
+ }
+}

sol/solution/0001-0100/0022/Solution.js

@@ -0,0 +1,21 @@
+/**
+ * @param {number} n
+ * @return {string[]}
+ */
+var generateParenthesis = function(n) {
+ var result = [];
+ var backtrack = function(current, open, close) {
+ if (current.length === n * 2) {
+ result.push(current);
+ return;
+ }
+ if (open < n) {
+ backtrack(current + '(', open + 1, close);
+ }
+ if (close < open) {
+ backtrack(current + ')', open, close + 1);
+ }
+ };
+ backtrack('', 0, 0);
+ return result;
+};