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114. Flatten Binary Tree to Linked List

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Роман Пытков
2026-03-25 23:18:30 +03:00
parent a8727e17a1
commit 6b483ea6d1
5 changed files with 131 additions and 0 deletions
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11
114. Flatten Binary Tree to Linked List/114. Flatten Binary Tree to Linked List.csproj Normal file
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@@ -0,0 +1,11 @@
<Project Sdk="Microsoft.NET.Sdk">
<PropertyGroup>
<OutputType>Exe</OutputType>
<TargetFramework>net10.0</TargetFramework>
<RootNamespace>_114._Flatten_Binary_Tree_to_Linked_List</RootNamespace>
<ImplicitUsings>enable</ImplicitUsings>
<Nullable>enable</Nullable>
</PropertyGroup>
</Project>

67
114. Flatten Binary Tree to Linked List/Program.cs Normal file
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@@ -0,0 +1,67 @@
var sol = new Solution();
var cases = new (int?[] input, int?[] expected)[]
{
(new int?[] { 1, 2, 5, 3, 4, null, 6 }, new int?[] { 1, null, 2, null, 3, null, 4, null, 5, null, 6 }),
// (Array.Empty<int?>(), Array.Empty<int?>()),
// (new int?[] { 0 }, new int?[] { 0 })
};
foreach (var (input, expected) in cases)
{
var root = BuildTreeFromLevelOrder(input);
if (root != null)
sol.Flatten(root);
var actual = FlattenToOutputList(root);
Console.WriteLine($"[{string.Join(", ", input.Select(FormatNullable))}] -> [{string.Join(", ", actual.Select(FormatNullable))}] (expected: [{string.Join(", ", expected.Select(FormatNullable))}])");
}
static TreeNode? BuildTreeFromLevelOrder(int?[] data)
{
if (data.Length == 0 || data[0] == null)
return null;
var root = new TreeNode(data[0].Value);
var queue = new Queue<TreeNode>();
queue.Enqueue(root);
var i = 1;
while (queue.Count > 0 && i < data.Length)
{
var node = queue.Dequeue();
if (i < data.Length && data[i] != null)
{
node.left = new TreeNode(data[i]!.Value);
queue.Enqueue(node.left);
}
i++;
if (i < data.Length && data[i] != null)
{
node.right = new TreeNode(data[i]!.Value);
queue.Enqueue(node.right);
}
i++;
}
return root;
}
static List<int?> FlattenToOutputList(TreeNode? root)
{
var result = new List<int?>();
var node = root;
while (node != null)
{
result.Add(node.val);
if (node.right != null)
result.Add(null);
node = node.right;
}
return result;
}
static string FormatNullable(int? value) => value?.ToString() ?? "null";

27
114. Flatten Binary Tree to Linked List/Solution.cs Normal file
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@@ -0,0 +1,27 @@
public class Solution
{
public void Flatten(TreeNode? root)
{
if (root == null)
return;
var head = root;
var stack = new Stack<TreeNode>();
if (root.right != null)
stack.Push(root.right);
if (root.left != null)
stack.Push(root.left);
while (stack.Count > 0)
{
var node = stack.Pop();
head.left = null;
head.right = node;
head = node;
if (node.right != null)
stack.Push(node.right);
if (node.left != null)
stack.Push(node.left);
}
}
}

12
114. Flatten Binary Tree to Linked List/TreeNode.cs Normal file
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@@ -0,0 +1,12 @@
public class TreeNode
{
public int val;
public TreeNode? left;
public TreeNode? right;
public TreeNode(int val = 0, TreeNode? left = null, TreeNode? right = null)
{
this.val = val;
this.left = left;
this.right = right;
}
}

14
Leetcode.sln
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@@ -193,6 +193,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "31. Next Permutation", "31.
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "32. Longest Valid Parentheses", "32. Longest Valid Parentheses\32. Longest Valid Parentheses.csproj", "{9BD247FC-E91E-4FBD-9E97-6B917E4606D2}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "114. Flatten Binary Tree to Linked List", "114. Flatten Binary Tree to Linked List\114. Flatten Binary Tree to Linked List.csproj", "{D86CCC06-597D-4DF8-8DCC-E7804E773530}"
EndProject
Global
GlobalSection(SolutionConfigurationPlatforms) = preSolution
Debug|Any CPU = Debug|Any CPU
@@ -1343,6 +1345,18 @@ Global
{9BD247FC-E91E-4FBD-9E97-6B917E4606D2}.Release|x64.Build.0 = Release|Any CPU
{9BD247FC-E91E-4FBD-9E97-6B917E4606D2}.Release|x86.ActiveCfg = Release|Any CPU
{9BD247FC-E91E-4FBD-9E97-6B917E4606D2}.Release|x86.Build.0 = Release|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Debug|Any CPU.Build.0 = Debug|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Debug|x64.ActiveCfg = Debug|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Debug|x64.Build.0 = Debug|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Debug|x86.ActiveCfg = Debug|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Debug|x86.Build.0 = Debug|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Release|Any CPU.ActiveCfg = Release|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Release|Any CPU.Build.0 = Release|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Release|x64.ActiveCfg = Release|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Release|x64.Build.0 = Release|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Release|x86.ActiveCfg = Release|Any CPU
{D86CCC06-597D-4DF8-8DCC-E7804E773530}.Release|x86.Build.0 = Release|Any CPU
EndGlobalSection
GlobalSection(SolutionProperties) = preSolution
HideSolutionNode = FALSE