Day10

116. Populating Next Right Pointers in Each Node/116. Populating Next Right Pointers in Each Node.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_116._Populating_Next_Right_Pointers_in_Each_Node</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

116. Populating Next Right Pointers in Each Node/Node.cs

@@ -0,0 +1,25 @@
+namespace _116._Populating_Next_Right_Pointers_in_Each_Node;
+
+// Definition for a Node.
+public class Node
+{
+    public int val;
+    public Node? left;
+    public Node? right;
+    public Node? next;
+
+    public Node() { }
+
+    public Node(int _val)
+    {
+        val = _val;
+    }
+
+    public Node(int _val, Node? _left, Node? _right, Node? _next)
+    {
+        val = _val;
+        left = _left;
+        right = _right;
+        next = _next;
+    }
+}

116. Populating Next Right Pointers in Each Node/Program.cs

@@ -0,0 +1,9 @@
+namespace _116._Populating_Next_Right_Pointers_in_Each_Node;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        Console.WriteLine("Hello, World!");
+    }
+}

116. Populating Next Right Pointers in Each Node/Solution.cs

@@ -0,0 +1,31 @@
+namespace _116._Populating_Next_Right_Pointers_in_Each_Node;
+
+public class Solution
+{
+    public Node? Connect(Node? root)
+    {
+        if (root == null)
+            return null;
+        List<Node> curLevel = new List<Node>() { root };
+        List<Node> nextLevel = new List<Node>();
+        while (curLevel.Count > 0)
+        {
+            for (int i = 0; i < curLevel.Count - 1; i++)
+                curLevel[i].next = curLevel[i + 1];
+            nextLevel.Clear();
+            foreach (var n in curLevel)
+            {
+                if (n == null)
+                    continue;
+                if (n.left != null)
+                    nextLevel.Add(n.left);
+                if (n.right != null)
+                    nextLevel.Add(n.right);
+            }
+            List<Node> buf = curLevel;
+            curLevel = nextLevel;
+            nextLevel = buf;
+        }
+        return root;
+    }
+}

144. Binary Tree Preorder Traversal/144. Binary Tree Preorder Traversal.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_144._Binary_Tree_Preorder_Traversal</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

144. Binary Tree Preorder Traversal/Program.cs

@@ -0,0 +1,9 @@
+namespace _144._Binary_Tree_Preorder_Traversal;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        Console.WriteLine("Hello, World!");
+    }
+}

144. Binary Tree Preorder Traversal/Solution.cs

@@ -0,0 +1,22 @@
+namespace _144._Binary_Tree_Preorder_Traversal;
+
+public class Solution
+{
+    public IList<int> PreorderTraversal(TreeNode root)
+    {
+        List<int> res = new List<int>();
+        Stack<TreeNode> stack = new Stack<TreeNode>();
+        if (root != null)
+            stack.Push(root);
+        while (stack.Count > 0)
+        {
+            TreeNode cur = stack.Pop();
+            if (cur.right != null)
+                stack.Push(cur.right);
+            if (cur.left != null)
+                stack.Push(cur.left);
+            res.Add(cur.val);
+        }
+        return res;
+    }
+}

144. Binary Tree Preorder Traversal/TreeNode.cs

@@ -0,0 +1,16 @@
+namespace _144._Binary_Tree_Preorder_Traversal;
+
+
+//Definition for a binary tree node.
+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;
+    }
+}

145. Binary Tree Postorder Traversal/145. Binary Tree Postorder Traversal.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_145._Binary_Tree_Postorder_Traversal</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

145. Binary Tree Postorder Traversal/Program.cs

@@ -0,0 +1,9 @@
+namespace _145._Binary_Tree_Postorder_Traversal;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        Console.WriteLine("Hello, World!");
+    }
+}

145. Binary Tree Postorder Traversal/Solution.cs

@@ -0,0 +1,24 @@
+namespace _145._Binary_Tree_Postorder_Traversal;
+
+public class Solution
+{
+    public IList<int> PostorderTraversal(TreeNode root)
+    {
+        var result = new List<int>();
+        if (root == null) return result;
+        var stack = new Stack<TreeNode>();
+        stack.Push(root);
+        while (stack.Any())
+        {
+            var cur = stack.Pop();
+            result.Add(cur.val);
+            if (cur.left != null)
+                stack.Push(cur.left);
+            if (cur.right != null)
+                stack.Push(cur.right);
+        }
+        result.Reverse();
+
+        return result;
+    }
+}

145. Binary Tree Postorder Traversal/TreeNode.cs

@@ -0,0 +1,16 @@
+namespace _145._Binary_Tree_Postorder_Traversal;
+
+
+//Definition for a binary tree node.
+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;
+    }
+}

200. Number of Islands/Solution.cs

@@ -1,6 +1,4 @@
-using System.ComponentModel;
-
-namespace _200._Number_of_Islands;
+namespace _200._Number_of_Islands;
 
 public class Solution
 {

235. Lowest Common Ancestor of a Binary Search Tree/Program.cs

@@ -7,6 +7,6 @@ internal class Program
         TreeNode root = new TreeNode(6);
         root.left = new TreeNode(2) { left = new TreeNode(0), right = new TreeNode(4) { left = new TreeNode(3), right = new TreeNode(5) } };
         root.right = new TreeNode(8) { left = new TreeNode(7), right = new TreeNode(9) };
-        Console.WriteLine(new Solution().LowestCommonAncestor(root, new TreeNode(3), new TreeNode(5)).val);
+        Console.WriteLine(new Solution().LowestCommonAncestor(root, new TreeNode(3), new TreeNode(5))?.val);
     }
 }

235. Lowest Common Ancestor of a Binary Search Tree/TreeNode.cs

@@ -1,7 +1,8 @@
 namespace _235._Lowest_Common_Ancestor_of_a_Binary_Search_Tree;
 
 //Definition for a binary tree node.
-public class TreeNode {
+public class TreeNode
+{
     public int val;
     public TreeNode? left;
     public TreeNode? right;

509. Fibonacci Number/509. Fibonacci Number.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_509._Fibonacci_Number</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

509. Fibonacci Number/Program.cs

@@ -0,0 +1,8 @@
+namespace _509._Fibonacci_Number;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+    }
+}

509. Fibonacci Number/Solution.cs

@@ -0,0 +1,20 @@
+namespace _509._Fibonacci_Number;
+
+public class Solution
+{
+    public int Fib(int n)
+    {
+        if (n == 0)
+            return 0;
+        n--;
+        int cur0 = 0;
+        int cur1 = 1;
+        while (--n > 0)
+        {
+            int buf = cur0 + cur1;
+            cur0 = cur1;
+            cur1 = buf;
+        }
+        return cur0 + cur1;
+    }
+}

617. Merge Two Binary Trees/617. Merge Two Binary Trees.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_617._Merge_Two_Binary_Trees</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

617. Merge Two Binary Trees/Program.cs

@@ -0,0 +1,58 @@
+namespace _617._Merge_Two_Binary_Trees;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        TreeNode root1 = new TreeNode(1);
+        root1.left = new TreeNode(3) { left = new TreeNode(5) };
+        root1.right = new TreeNode(2);
+
+
+        TreeNode root2 = new TreeNode(2);
+        root2.left = new TreeNode(1) { right = new TreeNode(4) };
+        root2.right = new TreeNode(3) { right = new TreeNode(7) };
+        var res = new Write().LevelOrder(new Solution().MergeTrees(root1, root2)!);
+        Console.WriteLine($"\nOutput");
+        foreach (var row in res)
+            Console.WriteLine(String.Join(" ", row));
+    }
+
+    public class Write
+    {
+        public IList<IList<int>> LevelOrder(TreeNode root)
+        {
+            List<IList<int>> output = new List<IList<int>>();
+            RecursiveTraversal(output, new List<TreeNode>() { root });
+            return output;
+        }
+
+        private void RecursiveTraversal(List<IList<int>> output, List<TreeNode> curLevel)
+        {
+            if (curLevel.Count == 0)
+                return;
+            List<int> levelValues = new List<int>();
+            foreach (var n in curLevel)
+            {
+                if (n == null)
+                    continue;
+                levelValues.Add(n.val);
+            }
+            if (levelValues.Count == 0)
+                return;
+            output.Add(levelValues);
+
+            List<TreeNode> nextLevel = new List<TreeNode>();
+            foreach (var n in curLevel)
+            {
+                if (n == null)
+                    continue;
+                if (n.left != null)
+                    nextLevel.Add(n.left);
+                if (n.right != null)
+                    nextLevel.Add(n.right);
+            }
+            RecursiveTraversal(output, nextLevel);
+        }
+    }
+}

617. Merge Two Binary Trees/Solution.cs

@@ -0,0 +1,31 @@
+namespace _617._Merge_Two_Binary_Trees;
+
+public class Solution
+{
+    public TreeNode? MergeTrees(TreeNode root1, TreeNode root2)
+    {
+        if (root1 == null && root2 == null)
+            return null;
+        else if (root1 == null)
+            return root2;
+        else if (root2 == null)
+            return root1;
+        var res = new TreeNode();
+        RecursionMerge(res, root1, root2);
+        return res;
+    }
+
+    private void RecursionMerge(TreeNode cur, TreeNode? t1, TreeNode? t2)
+    {
+        if (t1 != null)
+            cur.val += t1.val;
+        if (t2 != null)
+            cur.val += t2.val;
+        cur.left = (t1?.left != null || t2?.left != null) ? new TreeNode() : null;
+        cur.right = (t1?.right != null || t2?.right != null) ? new TreeNode() : null;
+        if (cur.left != null)
+            RecursionMerge(cur.left, t1?.left, t2?.left);
+        if (cur.right != null)
+            RecursionMerge(cur.right, t1?.right, t2?.right);
+    }
+}

617. Merge Two Binary Trees/TreeNode.cs

@@ -0,0 +1,16 @@
+namespace _617._Merge_Two_Binary_Trees;
+
+
+//Definition for a binary tree node.
+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;
+    }
+}

70. Climbing Stairs/70. Climbing Stairs.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_70._Climbing_Stairs</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

70. Climbing Stairs/Program.cs

@@ -0,0 +1,9 @@
+namespace _70._Climbing_Stairs;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        Console.WriteLine("Hello, World!");
+    }
+}

70. Climbing Stairs/Solution.cs

@@ -0,0 +1,19 @@
+namespace _70._Climbing_Stairs;
+
+public class Solution
+{
+    public int ClimbStairs(int n)
+    {
+        if (n == 0)
+            return 0;
+        int cur0 = 0;
+        int cur1 = 1;
+        while (--n > 0)
+        {
+            int buf = cur0 + cur1;
+            cur0 = cur1;
+            cur1 = buf;
+        }
+        return cur0 + cur1;
+    }
+}

94. Binary Tree Inorder Traversal/94. Binary Tree Inorder Traversal.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_94._Binary_Tree_Inorder_Traversal</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

94. Binary Tree Inorder Traversal/Program.cs

@@ -0,0 +1,9 @@
+namespace _94._Binary_Tree_Inorder_Traversal;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        Console.WriteLine("Hello, World!");
+    }
+}

94. Binary Tree Inorder Traversal/Solution.cs

@@ -0,0 +1,23 @@
+namespace _94._Binary_Tree_Inorder_Traversal;
+
+public class Solution
+{
+    public List<int> inorderTraversal(TreeNode root)
+    {
+        List<int> res = new List<int>();
+        Stack<TreeNode> stack = new Stack<TreeNode>();
+        TreeNode? curr = root;
+        while (curr != null || stack.Count > 0)
+        {
+            while (curr != null)
+            {
+                stack.Push(curr);
+                curr = curr.left;
+            }
+            curr = stack.Pop();
+            res.Add(curr.val);
+            curr = curr.right!;
+        }
+        return res;
+    }
+}

94. Binary Tree Inorder Traversal/TreeNode.cs

@@ -0,0 +1,15 @@
+namespace _94._Binary_Tree_Inorder_Traversal;
+
+//Definition for a binary tree node.
+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;
+    }
+}

Leetcode.sln

@@ -95,7 +95,21 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "98. Validate Binary Search
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "235. Lowest Common Ancestor of a Binary Search Tree", "235. Lowest Common Ancestor of a Binary Search Tree\235. Lowest Common Ancestor of a Binary Search Tree.csproj", "{B4466695-F56D-40E6-8D9C-D5955ACE8B4E}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "200. Number of Islands", "200. Number of Islands\200. Number of Islands.csproj", "{02FDE4A9-07D5-46B6-95AB-B61E1F3BA97B}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "200. Number of Islands", "200. Number of Islands\200. Number of Islands.csproj", "{02FDE4A9-07D5-46B6-95AB-B61E1F3BA97B}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "617. Merge Two Binary Trees", "617. Merge Two Binary Trees\617. Merge Two Binary Trees.csproj", "{79FEA33C-30E7-4FE6-A7C8-18BD13EE1B9A}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "116. Populating Next Right Pointers in Each Node", "116. Populating Next Right Pointers in Each Node\116. Populating Next Right Pointers in Each Node.csproj", "{DD19137E-1A2F-4803-910B-A63826F65159}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "144. Binary Tree Preorder Traversal", "144. Binary Tree Preorder Traversal\144. Binary Tree Preorder Traversal.csproj", "{0DA14E84-9F56-4384-9743-BA7FD7539113}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "94. Binary Tree Inorder Traversal", "94. Binary Tree Inorder Traversal\94. Binary Tree Inorder Traversal.csproj", "{60E8258E-4BBC-42C7-96CD-C67DB629E0E1}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "145. Binary Tree Postorder Traversal", "145. Binary Tree Postorder Traversal\145. Binary Tree Postorder Traversal.csproj", "{6E954C2F-608C-4294-91CF-62B8E49CC415}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "509. Fibonacci Number", "509. Fibonacci Number\509. Fibonacci Number.csproj", "{73450FFA-253B-42CC-B5E7-8769CFF1BE96}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "70. Climbing Stairs", "70. Climbing Stairs\70. Climbing Stairs.csproj", "{625340C0-FC67-4555-B49F-FB28E3177F72}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -291,6 +305,34 @@ Global
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 		{02FDE4A9-07D5-46B6-95AB-B61E1F3BA97B}.Release|Any CPU.Build.0 = Release|Any CPU
+		{79FEA33C-30E7-4FE6-A7C8-18BD13EE1B9A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{79FEA33C-30E7-4FE6-A7C8-18BD13EE1B9A}.Debug|Any CPU.Build.0 = Debug|Any CPU
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+		{79FEA33C-30E7-4FE6-A7C8-18BD13EE1B9A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{DD19137E-1A2F-4803-910B-A63826F65159}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{DD19137E-1A2F-4803-910B-A63826F65159}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{DD19137E-1A2F-4803-910B-A63826F65159}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{DD19137E-1A2F-4803-910B-A63826F65159}.Release|Any CPU.Build.0 = Release|Any CPU
+		{0DA14E84-9F56-4384-9743-BA7FD7539113}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{0DA14E84-9F56-4384-9743-BA7FD7539113}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{0DA14E84-9F56-4384-9743-BA7FD7539113}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{0DA14E84-9F56-4384-9743-BA7FD7539113}.Release|Any CPU.Build.0 = Release|Any CPU
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+		{60E8258E-4BBC-42C7-96CD-C67DB629E0E1}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{60E8258E-4BBC-42C7-96CD-C67DB629E0E1}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{60E8258E-4BBC-42C7-96CD-C67DB629E0E1}.Release|Any CPU.Build.0 = Release|Any CPU
+		{6E954C2F-608C-4294-91CF-62B8E49CC415}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{6E954C2F-608C-4294-91CF-62B8E49CC415}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{6E954C2F-608C-4294-91CF-62B8E49CC415}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{6E954C2F-608C-4294-91CF-62B8E49CC415}.Release|Any CPU.Build.0 = Release|Any CPU
+		{73450FFA-253B-42CC-B5E7-8769CFF1BE96}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{73450FFA-253B-42CC-B5E7-8769CFF1BE96}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{73450FFA-253B-42CC-B5E7-8769CFF1BE96}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{73450FFA-253B-42CC-B5E7-8769CFF1BE96}.Release|Any CPU.Build.0 = Release|Any CPU
+		{625340C0-FC67-4555-B49F-FB28E3177F72}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{625340C0-FC67-4555-B49F-FB28E3177F72}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{625340C0-FC67-4555-B49F-FB28E3177F72}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{625340C0-FC67-4555-B49F-FB28E3177F72}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE