如何使用递归迭代嵌套映射中的映射？

huangapple
go评论99阅读模式
英文:

How to iterate through a map of nested maps using recursion?

问题

我有嵌套的映射，需要遍历每个级别以打印所有的值。

这个映射是为了向您展示我正在尝试使用"递归"解决的问题的示例。

  1. MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::MainWindow) {
  2.     ui->setupUi(this);
  3.     std::map<std::string, VariableContainer> myMap;
  5.     for (int i = 0; i < 3; ++i) {
  6.         VariableContainer var;
  7.         var.variables["A" + std::to_string(i)];
  9.         if (i == 1) {
  10.             VariableContainer childVar;
  11.             for (int j = 1; j < 3; ++j) {
  12.                childVar.variables["X_" + std::to_string(j)];
  13.             }
  14.             var.variables.emplace("B" + std::to_string(i), childVar);
  15.         }
  16.         var.variables["C" + std::to_string(i)];
  17.         myMap.emplace("Node_" + std::to_string(i), var);
  18.     }
  20.     for (auto& var : myMap) {
  21.         std::cout << "var: " << var.first << std::endl;
  22.         if (var.second.variables.size() > 0) {
  23.             for (auto& child : var.second.variables) {
  24.                 std::cout << " child: " << child.first << std::endl;
  25.                 if (child.second.variables.size() > 0) {
  26.                     for (auto& subChild : child.second.variables) {
  27.                         std::cout << "  subChild: " << subChild.first << std::endl;
  28.                     }
  29.                 }
  30.             }
  31.         }
  32.     }
  33. }

这是输出：

  1. var: Node_0
  2.  child: A0
  3.  child: C0
  4. var: Node_1
  5.  child: A1
  6.  child: B1
  7.   subChild: X_1
  8.   subChild: X_2
  9.  child: C1
  10. var: Node_2
  11.  child: A2
  12.  child: C2

但我需要以以下结构输出：node + "." + child + "." + subChild + "." + nsubChilds

  1. Node_0.A0
  2. Node_0.C0
  3. Node_1.A1
  4. Node_1.B1.X_1
  5. Node_1.B1.X_2
  6. Node_1.C1
  7. Node_2.A2
  8. Node_2.C2

这是 VariableContainer.h：

  1. #ifndef VARIABLECONTAINER_H
  2. #define VARIABLECONTAINER_H
  4. #include <map>
  5. #include <string>
  7. class VariableContainer
  8. {
  9. public:
  10.     VariableContainer() {}
  11.     std::map<std::string, VariableContainer> variables;
  12. };
  14. #endif // VARIABLECONTAINER_H

我可以在其他映射中嵌套映射，类似于分支。我认为使用递归是一个好的解决方案，因为每次执行程序时嵌套映射的数量都不同。

例如，我可能有类似这样的内容：Node_1.B1.X_1.Y_1.Z_1

我尝试了以下递归函数，但没有获得期望的输出。

  1. void MainWindow::showMap(std::map<std::string, VariableContainer> &map) {
  2.     for (auto& var : map) {
  3.         std::cout << "var: " << var.first << std::endl;
  4.         if (var.second.variables.size() > 0) {
  5.             showMap(var.second.variables);
  6.         }
  7.     }
  8. }

有没有什么想法或建议来解决这个问题？

英文:

I have nested maps and I need to iterate through each level to print all the values.

This map is to show you an example of a problem that I am trying to solve using recursion.

  1. MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::MainWindow) {
  2.     ui-&gt;setupUi(this);
  3.     std::map&lt;std::string, VariableContainer&gt; myMap;
  5.     for (int i = 0; i &lt; 3; ++i) {
  6.         VariableContainer var;
  7.         var.variables[&quot;A&quot; + std::to_string(i)];
  9.         if (i == 1) {
  10.             VariableContainer childVar;
  11.             for (int j = 1; j &lt; 3; ++j) {
  12.                childVar.variables[&quot;X_&quot; + std::to_string(j)];
  13.             }
  14.             var.variables.emplace(&quot;B&quot; + std::to_string(i), childVar);
  15.         }
  16.         var.variables[&quot;C&quot; + std::to_string(i)];
  17.         myMap.emplace(&quot;Node_&quot; + std::to_string(i), var);
  18.     }
  20.     for (auto&amp; var : myMap) {
  21.         std::cout &lt;&lt; &quot;var: &quot;&lt;&lt; var.first &lt;&lt; std::endl;
  22.         if (var.second.variables.size()&gt;0) {
  23.             for (auto&amp; child : var.second.variables) {
  24.                 std::cout &lt;&lt; &quot; child: &quot;&lt;&lt; child.first &lt;&lt; std::endl;
  25.                 if (child.second.variables.size()&gt;0) {
  26.                     for (auto&amp; subChild : child.second.variables) {
  27.                         std::cout &lt;&lt; &quot;  subChild: &quot;&lt;&lt; subChild.first &lt;&lt; std::endl;
  28.                     }
  29.                 }
  30.             }
  31.         }
  32.     }
  33. }

This is the output:

  1. var: Node_0
  2.  child: A0
  3.  child: C0
  4. var: Node_1
  5.  child: A1
  6.  child: B1
  7.   subChild: X_1
  8.   subChild: X_2
  9.  child: C1
  10. var: Node_2
  11.  child: A2
  12.  child: C2

But I need to get the output in the following structure: node + &quot;.&quot; + child + &quot;.&quot; + subChild + &quot;.&quot; + nsubChilds

  1. Node_0.A0
  2. Node_0.C0
  3. Node_1.A1
  4. Node_1.B1.X_1
  5. Node_1.B1.X_2
  6. Node_1.C1
  7. Node_2.A2
  8. Node_2.C2

This is the VariableContainer.h

  1. #ifndef VARIABLECONTAINER_H
  2. #define VARIABLECONTAINER_H
  4. #include &lt;map&gt;
  5. #include &lt;string&gt;
  7. class VariableContainer
  8. {
  9. public:
  10.     VariableContainer() {}
  11.     std::map&lt;std::string, VariableContainer&gt; variables;
  12. };
  14. #endif // VARIABLECONTAINER_H

I could have maps nested within other maps, something like a branch. I think that using recursion is a good solution since the number of nested maps is different on each execution of the program.

For example, I could have something like this: Node_1.B1.X_1.Y_1.Z_1

I tried the following recursive function but I'm not getting the desired output.

  1. void MainWindow::showMap(std::map&lt;std::string, VariableContainer&gt; &amp;map) {
  2.     for (auto&amp; var : map) {
  3.         std::cout &lt;&lt; &quot;var: &quot;&lt;&lt; var.first &lt;&lt; std::endl;
  4.         if (var.second.variables.size() &gt; 0) {
  5.             showMap(var.second.variables);
  6.         }
  7.     }
  8. }

Any Idea or suggestion to solve this?

答案1

得分: 2

将分支名称传递给函数 showMap()。

例如：

  1. class VariableContainer
  2. {
  3. public:
  4.     VariableContainer() {}
  5.     std::map<std::string, VariableContainer> variables;
  6. };
  8. void showMap(
  9.     const std::string &BranchName,  //我认为这是必要的
  10.     const std::map<std::string, VariableContainer> &map
  11. )
  12. {
  13.     for (const auto &var : map)
  14.     {
  15.         std::string VarName = BranchName + var.first;
  16.         if (var.second.variables.empty())  //如果是叶子节点
  17.         {
  18.             std::cout << VarName << std::endl;
  19.         }
  20.         else
  21.         {
  22.             showMap(VarName + ".", var.second.variables);
  23.         }
  24.     }
  25. }
  27. inline void showMap(const std::map<std::string, VariableContainer> &map)
  28. {
  29.     showMap("", map);
  30. }
  32. int main(int argc, char *argv[])
  33. {
  34.     std::map<std::string, VariableContainer> Root;
  35.     {//构建测试数据
  36.         {
  37.             auto &Node_0 = Root["Node_0"].variables;
  38.             Node_0["A0"];
  39.             Node_0["C0"];
  40.         }
  41.         {
  42.             auto &Node_1 = Root["Node_1"].variables;
  43.             Node_1["A1"];
  44.             auto &B1 = Node_1["B1"].variables;
  45.             B1["X_1"];
  46.             B1["X_2"];
  47.         }
  48.         {
  49.             auto &Node_2 = Root["Node_2"].variables;
  50.             Node_2["A2"];
  51.             Node_2["C2"];
  52.         }
  53.     }
  55.     showMap(Root);
  56.     return 0;
  57. }

这是您提供的代码的翻译部分。

英文:

Pass the branch name to the function showMap().

e.g.

  1. class VariableContainer
  2. {
  3. public:
  4. 	VariableContainer() {}
  5. 	std::map&lt;std::string, VariableContainer&gt; variables;
  6. };
  8. void showMap(
  9. 	const std::string &amp;BranchName,  //I think this is necessary
  10. 	const std::map&lt;std::string, VariableContainer&gt; &amp;map
  11. )
  12. {
  13. 	for( const auto &amp;var : map )
  14. 	{
  15. 		std::string VarName = BranchName + var.first;
  16. 		if( var.second.variables.empty() )  //if leaf
  17. 		{	std::cout &lt;&lt; VarName &lt;&lt; std::endl;	}
  18. 		else
  19. 		{	showMap( VarName+&quot;.&quot;, var.second.variables );	}
  20. 	}
  21. }
  23. inline void showMap( const std::map&lt;std::string, VariableContainer&gt; &amp;map )
  24. {	showMap( &quot;&quot;, map );	}
  26. int main(int argc, char *argv[])
  27. {
  28. 	std::map&lt;std::string, VariableContainer&gt; Root;
  29. 	{//construct the test data
  30. 		{
  31. 			auto &amp;Node_0 = Root[&quot;Node_0&quot;].variables;
  32. 			Node_0[&quot;A0&quot;];
  33. 			Node_0[&quot;C0&quot;];
  34. 		}
  35. 		{
  36. 			auto &amp;Node_1 = Root[&quot;Node_1&quot;].variables;
  37. 			Node_1[&quot;A1&quot;];
  38. 			auto &amp;B1 = Node_1[&quot;B1&quot;].variables;
  39. 			B1[&quot;X_1&quot;];
  40. 			B1[&quot;X_2&quot;];
  41. 		}
  42. 		{
  43. 			auto &amp;Node_2 = Root[&quot;Node_2&quot;].variables;
  44. 			Node_2[&quot;A2&quot;];
  45. 			Node_2[&quot;C2&quot;];
  46. 		}
  47. 	}
  49. 	showMap( Root );
  50. 	return 0;
  51. }

huangapple
  • 本文由 发表于 2023年3月1日 08:50:01
  • 转载请务必保留本文链接：https://go.coder-hub.com/75598673.html
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