题目链接

22. 括号生成

思路

使用 DFS 和贪心的思想，如果左括号的数量不够就优先放置左括号，然后再放置右括号。

代码

class Solution {
    private List<String> result = new ArrayList<>();

    public List<String> generateParenthesis(int n) {

        if(n == 0){
            return this.result;
        }

        dfs(new StringBuilder(), 0, 0, n);

        return this.result;
    }

    void dfs(StringBuilder stringBuilder, int left, int right, int n){
        if(left == n && right == n){
            this.result.add(stringBuilder.toString());
            return;
        }

        if(left < right){
            return;
        }

        if(left < n){
            stringBuilder.append("(");
            dfs(stringBuilder, left + 1, right, n);
            stringBuilder.deleteCharAt(stringBuilder.length() - 1);
        }
        if(right < n){
            stringBuilder.append(")");
            dfs(stringBuilder, left, right + 1, n);
            stringBuilder.deleteCharAt(stringBuilder.length() - 1);
        }
    }
}