22. Generate Parentheses
Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.
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| class Solution {
bool valid(string& s) {
int st = 0;
for(auto& c: s) {
switch (c) {
case '(' : st++; break;
case ')' : st--; break;
}
if(st < 0) return false;
}
return st == 0;
}
public:
vector<string> generateParenthesis(int n) {
stringstream ss;
for(int i = 0; i < n; i++) ss << '(';
for(int i = 0; i < n; i++) ss << ')';
string s = ss.str();
vector<string> res;
do if(valid(s)){
res.push_back(s);
} while(next_permutation(begin(s), end(s)));
return res;
}
};
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