Generate Parentheses

题目

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:

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

方法

使用递归的思想。

    public void getParen(int left, int right, String str, List<String> list) {
        if (left == 0 && right == 0) {
            list.add(str);
        } else if (left == right) {
            str += "(";
            getParen(left - 1, right, str, list);
        } else {
            if (left > 0) {
                String strLeft = str + "(";
                getParen(left - 1, right, strLeft, list);
            }
            if (right > 0) {
                String strRight = str + ")";
                getParen(left, right - 1, strRight, list);
            }
        }
        
    }
    public List<String> generateParenthesis(int n) {
        List<String> list = new ArrayList<String>();
        String str = "";
        getParen(n, n , str, list);
        return list;
    }