Difficulty: Medium
Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
For example, given n = 3, a solution set is:
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| [
"((()))",
"(()())",
"(())()",
"()(())",
"()()()"
]
|
Solution
Language: Java
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| class Solution {
public List<String> generateParenthesis(int n) {
List<String> result = new ArrayList<>();
if (n <= 0) {
return result;
}
dfsHelper(n, result, new char[n * 2], 0, 0);
return result;
}
private void dfsHelper(int n, List<String> result, char[] chars, int index, int p) {
if (p < 0 || p > n) {
return;
}
if (index == chars.length) {
if (p == 0) {
result.add(new String(chars));
}
return;
}
chars[index] = '(';
dfsHelper(n, result, chars, index + 1, p + 1);
chars[index] = ')';
dfsHelper(n, result, chars, index + 1, p - 1);
}
}
|