leetcode 022 Generate Parentheses

题目

22. Generate Parentheses

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:

"((()))", "(()())", "(())()", "()(())", "()()()"

思路：

利用递归求解，递归这玩意不好解释，建议调试几次，追踪代码执行过程，用机器的方式去思考。

代码：

private List<String> list;

public List<String> generateParenthesis(int n)
{
String s = "";
list = new ArrayList<>();
generate(n, n, s);
return list;
}

void generate(int left, int right, String s)
{
if(left != 0)
{
generate(left - 1, right, s + "(");
if(left != right)
{
generate(left, right - 1, s + ")");
}
} else
{
if(right != 0)
{
int tmp = right;
StringBuilder builder = new StringBuilder(s);
while(tmp-- > 0)
builder.append(')');
list.add(builder.toString());
}
}
}

结果细节（图）：