[CareerCup]9.6 Generate Parenthesesかっこを生成
3136 ワード
9.6 Implement an algorithm to print all valid (e.g., properly opened and closed) combinations of n-pairs of parentheses.EXAMPLEInput: 3Output: ((())), (()()), (())(), ()(()), ()()()
LeetCodeの原題は、私の前のブログGenerate Parenthesesを参照してかっこを生成してください.
解法1:
class Solution {
public:
vector<string> generateParens(int n) {
set<string> t;
if (n == 0) t.insert("");
else {
vector<string> pre = generateParens(n - 1);
for (auto a : pre) {
for (int i = 0; i < a.size(); ++i) {
if (a[i] == '(') {
a.insert(a.begin() + i + 1, '(');
a.insert(a.begin() + i + 2, ')');
t.insert(a);
a.erase(a.begin() + i + 1, a.begin() + i + 3);
}
}
t.insert("()" + a);
}
}
return vector<string>(t.begin(), t.end());
}
};
解法2:
class Solution {
public:
vector<string> generateParens(int n) {
vector<string> res;
generateParensDFS(n, n, "", res);
return res;
}
void generateParensDFS(int left, int right, string out, vector<string> &res) {
if (left > right) return;
if (left == 0 && right == 0) res.push_back(out);
else {
if (left > 0) generateParensDFS(left - 1, right, out + '(', res);
if (right > 0) generateParensDFS(left, right - 1, out + ')', res);
}
}
};