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:

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

 

給定變量n，表示有n對括號，輸出n對括號全部正確匹配的狀況。

用遞歸來實現，left和right表示左右括號各剩下多少個，left >= right，即左括號剩下的多，則不能插入右括號。

public class Solution {
    private List<string> result = new List<string>();
    
    public IList<string> GenerateParenthesis(int n) 
    {
        string current = "";
        generate(n, n, current);
        return result;
    }
    
    public void generate(int left, int right, string current)//left 和 right 表示還剩下的左右括號的個數
    {
        if(left == 0 && right == 0)
        {
            result.Add(current);
            return;
        }
        if(left > 0)
        {
            generate(left - 1, right, current + "(");
        }
        if(right > 0 && left < right)
        {
            generate(left, right - 1, current + ")");
        }
    }
}