s0022

include/s0022_generate_parentheses.hpp

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+#ifndef S0022_GENERATE_PARENTHESES
+#define S0022_GENERATE_PARENTHESES
+
+#include <vector>
+#include <string>
+#include <cmath>
+
+using namespace std;
+
+class Solution {
+ public:
+  vector<string> generateParenthesis(int n);
+};
+
+#endif

src/s0022_generate_parentheses.cpp

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+#include "s0022_generate_parentheses.hpp"
+
+// 深度优先遍历:
+// 接收参数为每个节点的状态
+// 遍历结果可以用指针放在接收参数保存，也可以通过声明一个 class 的成员来保存
+void dfs(string current, int left, int right, vector<string> &result) {
+  // 讨论边界条件（结束条件）
+  // 不必讨论起始条件，因为初始化的工作会在 dfs 函数外完成。
+  if (left == 0 && right == 0) {
+    result.push_back(current);
+  }
+  // 讨论越界或不合法状态，剪枝
+  if (left > right) {
+    return;
+  }
+  // 合法状态，扩展到下一层
+  if (left > 0) {
+    dfs(current + '(', left - 1, right, result);
+  }
+  if (right > 0) {
+    dfs(current + ')', left, right - 1, result);
+  }
+}
+
+vector<string> Solution::generateParenthesis(int n) {
+  // 初始化
+  vector<string> result = {};
+  dfs("", n, n, result);
+  return result;
+}

tests/s0022_generate_parentheses.cpp

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+#include "s0022_generate_parentheses.hpp"
+
+#include <gtest/gtest.h>
+
+TEST(Problem22, Case1) {
+  int i{3};
+  vector<string> o{"((()))", "(()())", "(())()", "()(())", "()()()"};
+  Solution solution;
+  EXPECT_EQ(solution.generateParenthesis(i), o);
+}
+
+TEST(Problem22, Case2) {
+  int i{1};
+  vector<string> o{"()"};
+  Solution solution;
+  EXPECT_EQ(solution.generateParenthesis(i), o);
+}
+
+TEST(Problem22, Case3) {
+  int i{4};
+  vector<string> o{"(((())))","((()()))","((())())","((()))()","(()(()))","(()()())","(()())()","(())(())","(())()()","()((()))","()(()())","()(())()","()()(())","()()()()"};
+  Solution solution;
+  EXPECT_EQ(solution.generateParenthesis(i), o);
+}