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22.generate-parentheses

Statement

Metadata
  • Link: 括号生成
  • Difficulty: Medium
  • Tag: 字符串 动态规划 回溯

数字 n 代表生成括号的对数,请你设计一个函数,用于能够生成所有可能的并且 有效的 括号组合。

 

示例 1:

输入:n = 3
输出:["((()))","(()())","(())()","()(())","()()()"]

示例 2:

输入:n = 1
输出:["()"]

 

提示:

  • 1 <= n <= 8

Metadata

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

 

Example 1:

Input: n = 3
Output: ["((()))","(()())","(())()","()(())","()()()"]

Example 2:

Input: n = 1
Output: ["()"]

 

Constraints:

  • 1 <= n <= 8

Solution

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <string>
#include <vector>

#define endl "\n"
#define fi first
#define se second
#define all(x) begin(x), end(x)
#define rall rbegin(a), rend(a)
#define bitcnt(x) (__builtin_popcountll(x))
#define complete_unique(a) a.erase(unique(begin(a), end(a)), end(a))
#define mst(x, a) memset(x, a, sizeof(x))
#define MP make_pair

using ll = long long;
using ull = unsigned long long;
using db = double;
using ld = long double;
using VLL = std::vector<ll>;
using VI = std::vector<int>;
using PII = std::pair<int, int>;
using PLL = std::pair<ll, ll>;

using namespace __gnu_pbds;
using namespace std;
template <typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

template <typename T, typename S>
inline bool chmax(T &a, const S &b) {
    return a < b ? a = b, 1 : 0;
}

template <typename T, typename S>
inline bool chmin(T &a, const S &b) {
    return a > b ? a = b, 1 : 0;
}

#ifdef LOCAL
#include <debug.hpp>
#else
#define dbg(...)
#endif
// head

class Solution {
public:
    vector<string> generateParenthesis(int n) {
        const auto ok = [](const string &s) {
            int l = 0;

            for (const char &c : s) {
                if (c == '(') {
                    ++l;
                } else {
                    if (!l) {
                        return false;
                    }
                    --l;
                }
            }

            return !l;
        };

        auto res = vector<string>();
        n <<= 1;

        for (int S = 0; S < 1 << n; S++) {
            auto s = string();

            for (int i = 0; i < n; i++) {
                s += string(1, (S >> i & 1) ? '(' : ')');
            }

            if (ok(s)) {
                res.push_back(s);
            }
        }

        return res;
    }
};

#ifdef LOCAL

int main() {
    return 0;
}

#endif

最后更新: January 15, 2023
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