Leetcode: Generate Parentheses

最新推荐文章于 2020-02-06 12:14:11 发布

原创最新推荐文章于 2020-02-06 12:14:11 发布 · 670 阅读

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本文介绍了一种生成有效括号组合的算法。该算法通过递归方式生成所有可能的括号序列，并确保任何时候左括号数量不少于右括号数量，以此避免无效序列。通过这种方法，可以高效地生成所有长度为2n的有效括号序列。

http://oj.leetcode.com/problems/generate-parentheses/

// Interesting questions
// It is very easy to generate duplicated result with normal dp
// The core idea is that from the start to the end of the string,
// we need to keep the property that cnt("(") is more than or equal to cnt(")")
class Solution {
public:
    void Generate(int left, int right, string current, vector<string> &res){
        if(left==0&&right==0) res.push_back(current);
        if(left>0) Generate(left-1,right,current+"(",res);
        if(right>left) Generate(left,right-1,current+")",res);
    }
    vector<string> generateParenthesis(int n) {
        vector<string> res;
        Generate(n,n,"",res);
        return res;
    }
};