22. Generate Parentheses

[Shawngbk]

递归实现，如果左括号还有剩余，则可以放置左括号，如果右括号的剩余数大于左括号，则可以放置右括号。

public class Solution { public List generateParenthesis(int n) { ArrayList res = new ArrayList(); generateRes(n, n, "", res); return res; }

private void generateRes(int left, int right, String str, ArrayList<String> res) {
    if(left == 0 && right == 0) {
        res.add(str);
        return;
    }
    if(left > 0) {
        generateRes(left - 1, right, str + '(', res);
    }
    if(right > left) {
        generateRes(left, right - 1, str + ')', res);
    }
}

}

[Shawngbk]

考