【leetcode】22. Generate Parentheses

最新推荐文章于 2021-08-27 14:30:10 发布

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最新推荐文章于 2021-08-27 14:30:10 发布

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分类专栏：【leetcode】文章标签： leetcode dfs

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dfs，只要 ( 的数量小于 ) 的数量，即可以不断的dfs

/**
 * @author          johnsondu
 * @problem         Generate Parentheses
 * @url             https://leetcode.com/problems/generate-parentheses/
 * @strategy        dfs, only if left "(" less than right ")",  then it is legal.
 * @status          Accepted, runtime beats 34.01% of cpp submissions. 0ms
 * @time            19:46, Nov 3th 2015
 */

class Solution {
public:
    void dfs(string tmp, int lf, int rt, vector<string>& ans)
    {
        if(lf == 0 && rt == 0) {
            ans.push_back(tmp);
        }    
        if(lf != 0 && lf <= rt) {
            dfs(tmp + "(", lf - 1, rt, ans);
        } 
        if(lf < rt) {
            dfs(tmp + ")", lf, rt - 1, ans);
        }
    }
    
    vector<string> generateParenthesis(int n) {
        vector<string> ans;
        if(n == 0) return ans;
        dfs("(", n-1, n, ans);
        return ans;
    }
};