Day3. Start Algorithm

1. Two Sum/Solution.cs

@@ -1,10 +1,4 @@
-using System;
+namespace _1._Two_Sum;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace _1._Two_Sum;
 
 public class Solution
 {

121. Best Time to Buy and Sell Stock/121. Best Time to Buy and Sell Stock.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_121._Best_Time_to_Buy_and_Sell_Stock</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

121. Best Time to Buy and Sell Stock/Program.cs

@@ -0,0 +1,10 @@
+namespace _121._Best_Time_to_Buy_and_Sell_Stock
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.WriteLine(new Solution().MaxProfit(new int[] { 7, 1, 5, 3, 6, 4 }));
+        }
+    }
+}

121. Best Time to Buy and Sell Stock/Solution.cs

@@ -0,0 +1,27 @@
+namespace _121._Best_Time_to_Buy_and_Sell_Stock;
+
+public class Solution
+{
+    public int MaxProfit(int[] prices)
+    {
+        int min = prices[0];
+        int max = prices[0];
+        bool hasMax = false;
+        int res = 0;
+        foreach (int price in prices)
+        {
+            if (price > max || hasMax == false)
+            {
+                max = price;
+                hasMax = true;
+                res = Math.Max(max - min, res);
+            }
+            if (price < min)
+            {
+                min = price;
+                hasMax = false;
+            }
+        }
+        return res > 0 ? res : 0;
+    }
+}

1480. Running Sum of 1d Array/Solution.cs

@@ -1,10 +1,4 @@
-using System;
+namespace _1480._Running_Sum_of_1d_Array;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace _1480._Running_Sum_of_1d_Array;
 
 public class Solution
 {

205. Isomorphic Strings/Solution.cs

@@ -1,10 +1,4 @@
-using System;
+namespace _205._Isomorphic_Strings;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace _205._Isomorphic_Strings;
 
 public class Solution
 {

206. Reverse Linked List/206. Reverse Linked List.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_206._Reverse_Linked_List</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

206. Reverse Linked List/ListNode.cs

@@ -0,0 +1,36 @@
+namespace _206._Reverse_Linked_List;
+//Definition for singly-linked list.
+public class ListNode
+{
+    public int val;
+    public ListNode? next;
+    public ListNode(int val = 0, ListNode? next = null)
+    {
+        this.val = val;
+        this.next = next;
+    }
+
+    public static ListNode Create(int[] nums)
+    {
+        ListNode l = new ListNode(nums[0]);
+        ListNode cur = l;
+        for (int i = 1; i < nums.Length; i++)
+        {
+            cur.next = new ListNode(nums[i]);
+            cur = cur.next;
+        }
+        return l;
+    }
+
+    public override string ToString()
+    {
+        List<int> list = new List<int>();
+        ListNode? cur = this;
+        while (cur != null)
+        {
+            list.Add(cur.val);
+            cur = cur.next;
+        }
+        return String.Join(" ", list);
+    }
+}

206. Reverse Linked List/Program.cs

@@ -0,0 +1,11 @@
+namespace _206._Reverse_Linked_List
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            var l = ListNode.Create(new int[] { 1 });
+            Console.WriteLine(new Solution().ReverseList(l));
+        }
+    }
+}

206. Reverse Linked List/Solution.cs

@@ -0,0 +1,22 @@
+namespace _206._Reverse_Linked_List;
+
+public class Solution
+{
+    public ListNode? ReverseList(ListNode head)
+    {
+        if (head == null || head.next == null)
+            return head;
+        ListNode cur = head;
+        ListNode newHead = cur.next!;
+        cur.next = null;
+        while (true)
+        {
+            ListNode? buf = newHead.next;
+            newHead.next = cur;
+            if (buf == null)
+                return newHead;
+            cur = newHead;
+            newHead = buf;
+        }
+    }
+}

21. Merge Two Sorted Lists/21. Merge Two Sorted Lists.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_21._Merge_Two_Sorted_Lists</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

21. Merge Two Sorted Lists/ListNode.cs

@@ -0,0 +1,37 @@
+namespace _21._Merge_Two_Sorted_Lists;
+
+//Definition for singly-linked list.
+public class ListNode
+{
+    public int val;
+    public ListNode? next;
+    public ListNode(int val = 0, ListNode? next = null)
+    {
+        this.val = val;
+        this.next = next;
+    }
+
+    public static ListNode Create(int[] nums)
+    {
+        ListNode l = new ListNode(nums[0]);
+        ListNode cur = l;
+        for (int i = 1; i < nums.Length; i++)
+        {
+            cur.next = new ListNode(nums[i]);
+            cur = cur.next;
+        }
+        return l;
+    }
+
+    public override string ToString()
+    {
+        List<int> list = new List<int>();
+        ListNode? cur = this;
+        while (cur != null)
+        {
+            list.Add(cur.val);
+            cur = cur.next;
+        }
+        return String.Join(" ", list);
+    }
+}

21. Merge Two Sorted Lists/Program.cs

@@ -0,0 +1,12 @@
+namespace _21._Merge_Two_Sorted_Lists
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            var l1 = ListNode.Create(new int[] { 1, 2, 4 });
+            var l2 = ListNode.Create(new int[] { 1, 3, 4 });
+            Console.WriteLine(new Solution().MergeTwoLists(l1, l2));
+        }
+    }
+}

21. Merge Two Sorted Lists/Solution.cs

@@ -0,0 +1,44 @@
+namespace _21._Merge_Two_Sorted_Lists;
+
+public class Solution
+{
+    public ListNode MergeTwoLists(ListNode? list1, ListNode? list2)
+    {
+        ListNode? start = null;
+        ListNode? current = null;
+        List<ListNode?> listNodes = new List<ListNode?>() { list1, list2 };
+        while (listNodes.Any(l => l != null))
+        {
+            int i = MinIndex(listNodes);
+            ListNode? curMin = listNodes[i];
+            listNodes[i] = listNodes[i]!.next;
+
+            if (start == null)
+            {
+                start = curMin;
+                current = start;
+            }
+            else if (current != null)
+            {
+                current.next = curMin;
+                current = current.next;
+            }
+        }
+        return start!;
+    }
+
+    private int MinIndex(List<ListNode?> list)
+    {
+        int minValue = int.MaxValue;
+        int index = -1;
+        for (int i = 0; i < list.Count; i++)
+        {
+            if (list[i]?.val < minValue)
+            {
+                minValue = list[i]!.val;
+                index = i;
+            }
+        }
+        return index;
+    }
+}

278. First Bad Version/278. First Bad Version.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_278._First_Bad_Version</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

278. First Bad Version/Program.cs

@@ -0,0 +1,10 @@
+namespace _278._First_Bad_Version
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.WriteLine(new Solution().FirstBadVersion(2147483647, 2147483647));
+        }
+    }
+}

278. First Bad Version/Solution.cs

@@ -0,0 +1,33 @@
+namespace _278._First_Bad_Version;
+
+public class VersionControl
+{
+    protected int _badVersion = 0;
+    protected bool IsBadVersion(int version) => version >= _badVersion;
+}
+
+public class Solution : VersionControl
+{
+    public int FirstBadVersion(int n)
+    {
+        long l = -1;
+        long r = n;
+        while (l != r - 1)
+        {
+            long i = (r + l) / 2;
+            bool res = IsBadVersion((int)i);
+            if (res)
+                r = i;
+            else
+                l = i;
+        }
+        return (int)l + 1;
+    }
+
+    public int FirstBadVersion(int n, int bad)
+    {
+        _badVersion = bad;
+        return FirstBadVersion(n);
+    }
+}
+

35. Search Insert Position/35. Search Insert Position.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_35._Search_Insert_Position</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

35. Search Insert Position/Program.cs

@@ -0,0 +1,10 @@
+namespace _35._Search_Insert_Position
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.WriteLine("Hello, World!");
+        }
+    }
+}

35. Search Insert Position/Solution.cs

@@ -0,0 +1,19 @@
+namespace _35._Search_Insert_Position;
+
+public class Solution
+{
+    public int SearchInsert(int[] nums, int target)
+    {
+        int l = -1;
+        int r = nums.Length;
+        while (l != r - 1)
+        {
+            int i = (r + l) / 2;
+            if (nums[i] >= target)
+                r = i;
+            else
+                l = i;
+        }
+        return l + 1;
+    }
+}

350. Intersection of Two Arrays II/Solution.cs

@@ -4,6 +4,24 @@ public class Solution
 {
     public int[] Intersect(int[] nums1, int[] nums2)
     {
+        List<int> result = new List<int>();
+        Dictionary<int, int> table = new Dictionary<int, int>();
+        foreach (int n in nums1)
+        {
+            if (table.ContainsKey(n))
+                table[n]++;
+            else
+                table.Add(n, 1);
+        }
 
+        foreach (int n in nums2)
+        {
+            if (table.ContainsKey(n) && table[n] > 0)
+            {
+                result.Add(n);
+                table[n]--;
+            }
+        }
+        return result.ToArray();
     }
 }

392. Is Subsequence/Solution.cs

@@ -1,10 +1,4 @@
-using System;
+namespace _392._Is_Subsequence;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace _392._Is_Subsequence;
 
 public class Solution
 {

704. Binary Search/704. Binary Search.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_704._Binary_Search</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

704. Binary Search/Program.cs

@@ -0,0 +1,10 @@
+namespace _704._Binary_Search
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.WriteLine(new Solution().Search(new int[] { -1, 0, 3, 5, 9, 12 }, 13));
+        }
+    }
+}

704. Binary Search/Solution.cs

@@ -0,0 +1,22 @@
+namespace _704._Binary_Search;
+
+public class Solution
+{
+    public int Search(int[] nums, int target)
+    {
+        int l = -1;
+        int r = nums.Length;
+        while (l < r - 1)
+        {
+            int i = l + (r - l) / 2;
+            int cur = nums[i];
+            if (cur == target)
+                return i;
+            if (cur > target)
+                r = i;
+            else
+                l = i;
+        }
+        return -1;
+    }
+}

724. Find Pivot Index/Solution.cs

@@ -1,10 +1,4 @@
-using System;
+namespace _724._Find_Pivot_Index;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace _724._Find_Pivot_Index;
 
 public class Solution
 {

88. Merge Sorted Array/Solution.cs

@@ -1,8 +1,4 @@
-using System;
+namespace _88._Merge_Sorted_Array;
-using System.Collections.Generic;
-using System.Linq;
-
-namespace _88._Merge_Sorted_Array;
 
 public class Solution
 {

Leetcode.sln

@@ -19,7 +19,19 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "205. Isomorphic Strings", "
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "392. Is Subsequence", "392. Is Subsequence\392. Is Subsequence.csproj", "{82D9F372-85D0-4293-932D-6F90D4AF9CBD}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "350. Intersection of Two Arrays II", "350. Intersection of Two Arrays II\350. Intersection of Two Arrays II.csproj", "{3EDA43F9-22B1-4CFE-9912-031FFAA2200E}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "350. Intersection of Two Arrays II", "350. Intersection of Two Arrays II\350. Intersection of Two Arrays II.csproj", "{3EDA43F9-22B1-4CFE-9912-031FFAA2200E}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "121. Best Time to Buy and Sell Stock", "121. Best Time to Buy and Sell Stock\121. Best Time to Buy and Sell Stock.csproj", "{79A12189-DF47-4F0B-ADB1-A5FD930AE7EB}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "21. Merge Two Sorted Lists", "21. Merge Two Sorted Lists\21. Merge Two Sorted Lists.csproj", "{3063143F-AAF9-4B23-8D98-A7236E01AA27}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "206. Reverse Linked List", "206. Reverse Linked List\206. Reverse Linked List.csproj", "{1C1BEA62-325F-48F8-8CC0-D5828A62F14F}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "704. Binary Search", "704. Binary Search\704. Binary Search.csproj", "{69081812-D523-4211-AE09-9DAF8E9B83D8}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "278. First Bad Version", "278. First Bad Version\278. First Bad Version.csproj", "{3BA31E13-3748-4C4A-BE68-24D2E3DF0DC1}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "35. Search Insert Position", "35. Search Insert Position\35. Search Insert Position.csproj", "{B595BB51-666D-4E39-86EE-F9A3B8D8DA58}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -63,6 +75,30 @@ Global
 		{3EDA43F9-22B1-4CFE-9912-031FFAA2200E}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{3EDA43F9-22B1-4CFE-9912-031FFAA2200E}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{3EDA43F9-22B1-4CFE-9912-031FFAA2200E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{79A12189-DF47-4F0B-ADB1-A5FD930AE7EB}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{79A12189-DF47-4F0B-ADB1-A5FD930AE7EB}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{79A12189-DF47-4F0B-ADB1-A5FD930AE7EB}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{79A12189-DF47-4F0B-ADB1-A5FD930AE7EB}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3063143F-AAF9-4B23-8D98-A7236E01AA27}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3063143F-AAF9-4B23-8D98-A7236E01AA27}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3063143F-AAF9-4B23-8D98-A7236E01AA27}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3063143F-AAF9-4B23-8D98-A7236E01AA27}.Release|Any CPU.Build.0 = Release|Any CPU
+		{1C1BEA62-325F-48F8-8CC0-D5828A62F14F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{1C1BEA62-325F-48F8-8CC0-D5828A62F14F}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{1C1BEA62-325F-48F8-8CC0-D5828A62F14F}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{1C1BEA62-325F-48F8-8CC0-D5828A62F14F}.Release|Any CPU.Build.0 = Release|Any CPU
+		{69081812-D523-4211-AE09-9DAF8E9B83D8}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{69081812-D523-4211-AE09-9DAF8E9B83D8}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{69081812-D523-4211-AE09-9DAF8E9B83D8}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{69081812-D523-4211-AE09-9DAF8E9B83D8}.Release|Any CPU.Build.0 = Release|Any CPU
+		{3BA31E13-3748-4C4A-BE68-24D2E3DF0DC1}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{3BA31E13-3748-4C4A-BE68-24D2E3DF0DC1}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{3BA31E13-3748-4C4A-BE68-24D2E3DF0DC1}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{3BA31E13-3748-4C4A-BE68-24D2E3DF0DC1}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B595BB51-666D-4E39-86EE-F9A3B8D8DA58}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B595BB51-666D-4E39-86EE-F9A3B8D8DA58}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B595BB51-666D-4E39-86EE-F9A3B8D8DA58}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B595BB51-666D-4E39-86EE-F9A3B8D8DA58}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE