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:
"((()))", "(()())", "(())()", "()(())", "()()()"
public class Solution {
public List<String> generateParenthesis(int n) {
List<String> result = new ArrayList<String>();
solve(0, 0, n, result, "");
System.out.println(result);
return result;
}
void solve(int left,int right,int n,List<String> result,String str){
if(left<right) return;//left括号数目一定要比右边多
if(left==n && right==n){//如果左右括号数目相等则添加到list
result.add(str);
return;
}
if(left==n){//左括号已满,只能添加右括号
solve(left, right+1, n, result, str+")");
return;
}
solve(left+1, right, n, result, str+"(");//继续添加左括号
solve(left, right+1, n, result, str+")");//继续添加右括号
}
}