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leetcode_22.cpp
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leetcode_22.cpp
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class Solution {
public:
void dfs(int n, int left, int right, string path, vector<string>& ret){
if (left > n or right > n or right > left) return;
if (right == n){
ret.push_back(path);
return;
}
path.push_back('(');
dfs(n, left + 1, right, path, ret);
path.pop_back();
path.push_back(')');
dfs(n, left, right + 1, path, ret);
return;
}
vector<string> generateParenthesis(int n) {
string path;
vector<string> ret;
dfs(n, 0, 0, path, ret);
return ret;
}
};
class Solution {
public:
vector<string> generateParenthesis(int n) {
if (n == 1){
vector<string> ret = {"()"};
return ret;
}
set<string> hash;
vector<string> last = generateParenthesis(n - 1);
for (int i = 0; i < last.size(); i++){
for (int j = 0; j < last[i].size();j++){
string temp = last[i].substr(0, j) + "()" + last[i].substr(j);
hash.insert(temp);
}
}
vector<string> ret(hash.begin(), hash.end());
return ret;
}
};