Posts Tagged 【dfs】Generate Parentheses

最新推荐文章于 2022-02-26 16:45:31 发布

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本文介绍了一个使用深度优先搜索(DFS)算法生成所有有效括号组合的方法。针对输入的整数n，该算法能够生成所有可能的有效括号组合，例如当n为3时，输出包括((()))、(()())等五种不同的组合。

Generate Parentheses

Total Accepted: 41747 Total Submissions: 128780 My Submissions

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

For example, given n = 3, a solution set is:

"((()))", "(()())", "(())()", "()(())", "()()()"

/*
深搜DFS的思路
递归的思路
*/
public class Solution {
    public List<String> generateParenthesis(int n) {
        List<String> list = new ArrayList<String>();
        StringBuilder str = new StringBuilder();
        generate(list,str,0,0,2*n);
        return list;
    }
    private void generate(List<String> list,StringBuilder str,int left,int right,int n) {
        if(left + right == n) {
        	if(left == right) {
                list.add(str.toString());
        	}
            return;
        }
        if(left+right < n && left > right) {
        	if(str.length() < left+right+1)
        		str.append(')');
        	else {
            	str.setCharAt(left+right, ')');       		
        	}
            generate(list,str,left,right+1,n);
        }
        if(str.length() < left+right+1)
    		str.append('(');
    	else {
        	str.setCharAt(left+right, '(');       		
    	}
        generate(list,str,left+1,right,n);
    }
}

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