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：
题目意思是给一个整形数字，返回合法左右括号这种组合的所有组合，典型的使用回溯法来做。
代码：
java：
代码语言：javascript复制class Solution {
public List<String> generateParenthesis(int n) {
List<String> res = new ArrayList<String>();
backtrack(res, "", 0, 0, n);
return res;
}
private void backtrack(List<String> res, String s, int left, int right, int max) {
if (s.length() == max *2) {
res.add(s);
return;
}
if (left < max) {
backtrack(res, s "(", left 1, right, max);
}
if (right < left) {
backtrack(res, s ")", left, right 1, max);
}
}
}
