LeetCode-in-Dart
22. Generate Parentheses
Medium
Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
Example 1:
Input: n = 3
Output: [”((()))”,”(()())”,”(())()”,”()(())”,”()()()”]
Example 2:
Input: n = 1
Output: [”()”]
Constraints:
1 <= n <= 8
Solution
class Solution {
List<String> generateParenthesis(int n) {
return parenthesis(n, n);
}
List<String> parenthesis(int left, int right) {
if (left == 0 && right == 0) {
return [""];
}
List<String> return_ls = [];
if (left != 0) {
List<String> l1 = parenthesis(left - 1, right);
for (int i = 0; i < l1.length; ++i) {
l1[i] = '(' + l1[i];
return_ls.add(l1[i]);
}
}
if (right != 0 && left < right) {
List<String> r1 = parenthesis(left, right - 1);
for (int i = 0; i < r1.length; ++i) {
r1[i] = ')' + r1[i];
return_ls.add(r1[i]);
}
}
return return_ls;
}
}