【Hot100】22. bracket-generating

22. Bracket generation
Medium question
Numbers n Represents the logarithm of the generated bracket , Please design a function , Used to be able to generate all possible and Effective Bracket combination .

Reference resources ：https://leetcode.cn/problems/generate-parentheses/solution/zui-jian-dan-yi-dong-de-dong-tai-gui-hua-bu-lun-da/
Dynamic programming

class Solution {
    
    public List<String> generateParenthesis(int n) {
    
        List<List<String>> res = new LinkedList<>();
        res.add(new LinkedList<>(Arrays.asList("")));
        res.add(new LinkedList<>(Arrays.asList("()")));
        for (int i = 2; i <= n; i++) {
    
            List<String> tmp = new LinkedList<>();
            for (int j = 0; j < i; j++) {
    
                List<String> str1 = res.get(j);
                List<String> str2 = res.get(i - 1 - j);
                for (String s1 : str1) {
    
                    for (String s2 : str2) {
    
                        String str = "(" + s1 + ")" + s2;
                        tmp.add(str);
                    }
                }
            }
            res.add(tmp);
        }
        return res.get(n);
    }
}