对于每个位置我们都有两种选择(放左括号或右括号),为了生成有效的括号,右括号剩余个数要比左括号的剩余个数大才能放右括号。
class Solution {
vector<string>v;
public:
vector<string> generateParenthesis(int n){
dfs(n,n,"");
return v;
}
void dfs(int left,int right,string s)
{
if(left == 0 && right == 0)
{
v.push_back(s);
return;
}
if(left > 0)
{
dfs(left-1,right,s + '(');
}
if(right > left)
dfs(left,right-1,s + ')');
}
};