LeetCode题解22:Generate Parentheses

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:

”((()))”, “(()())”, “(())()”, “()(())”, “()()()”

题解:

这个没什么说的，就是递归遍历即可，注意一点，当此时右括号数目大于左括号数目时不能插入右括号了，相当于一个剪枝吧

Java 代码:

public List<String> generateParenthesis(int n) {
    
    List<String> result = new ArrayList<String>();
	generate(result, "", 0, 0, n);
	return result;
}


/**
l为左括号数目，r为右括号数目
*/
private void generate(List<String> result, String temp, int l, int r, int n) {
	
	if (l == n) {
		for (int i = 0; i < n - r; i++)
			temp += ")";
		
		result.add(temp);
		return;
	}
	
	generate(result, temp + "(", l + 1, r, n);
	if (r < l)
		generate(result, temp + ")", l, r + 1, n);
		
	
}

Written on January 15, 2016