力扣22. 括号生成

Posted 2021-06-27 幽殇默

题目地址

class Solution {
public:
    vector<string> ve;
    vector<string> generateParenthesis(int n) {
        dfs(1,n,"");
        return ve;
    }
    void dfs(int index,int n,string s)
    {
	    if(index==n*2+1)
	    {
		    stack<char>st;
		    for(int i=0;i<s.size();i++)
		    {
			    if(st.size())
			    {
			    	if( st.top()=='('&&s[i]==')') st.pop();
				    else st.push(s[i]);
			    }
			    else st.push(s[i]);
		    }
		    if(st.size()==0) ve.push_back(s);
		    return ;
	    }
	    dfs(index+1,n,s+"(");
	    dfs(index+1,n,s+")");
    }
};

y总方法:

class Solution {
public:
    vector<string> ve;
    vector<string> generateParenthesis(int n) {
        dfs(n,0,0,"");
        return ve;
    }
    void dfs(int n,int l,int r,string s)
    {
	    if(l==n&&r==n) ve.push_back(s);
        else
        {
            if(l<n) dfs(n,l+1,r,s+"(");
            if(l>r) dfs(n,l,r+1,s+")");//左括号数量大于右括号
        }
    }
};