tuantai0708

.gitignore

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+# The following command works for downloading when using Git for Windows:
+# curl -LOf http://gist.githubusercontent.com/kmorcinek/2710267/raw/.gitignore
+#
+# Download this file using PowerShell v3 under Windows with the following comand:
+# Invoke-WebRequest https://gist.githubusercontent.com/kmorcinek/2710267/raw/ -OutFile .gitignore
+#
+# or wget:
+# wget --no-check-certificate http://gist.githubusercontent.com/kmorcinek/2710267/raw/.gitignore
+
+# User-specific files
+*.suo
+*.user
+*.sln.docstates
+
+# Build results
+[Dd]ebug/
+[Rr]elease/
+x64/
+[Bb]in/
+[Oo]bj/
+# build folder is nowadays used for build scripts and should not be ignored
+#build/
+
+# NuGet Packages
+*.nupkg
+# The packages folder can be ignored because of Package Restore
+**/packages/*
+# except build/, which is used as an MSBuild target.
+!**/packages/build/
+# Uncomment if necessary however generally it will be regenerated when needed
+#!**/packages/repositories.config
+
+# MSTest test Results
+[Tt]est[Rr]esult*/
+[Bb]uild[Ll]og.*
+
+*_i.c
+*_p.c
+*.ilk
+*.meta
+*.obj
+*.pch
+*.pdb
+*.pgc
+*.pgd
+*.rsp
+*.sbr
+*.tlb
+*.tli
+*.tlh
+*.tmp
+*.tmp_proj
+*.log
+*.vspscc
+*.vssscc
+.builds
+*.pidb
+*.scc
+
+# Visual C++ cache files
+ipch/
+*.aps
+*.ncb
+*.opensdf
+*.sdf
+*.cachefile
+
+# Visual Studio profiler
+*.psess
+*.vsp
+*.vspx
+*.sln
+*.csproj
+
+# Guidance Automation Toolkit
+*.gpState
+
+# ReSharper is a .NET coding add-in
+_ReSharper*/
+*.[Rr]e[Ss]harper
+
+# TeamCity is a build add-in
+_TeamCity*
+
+# DotCover is a Code Coverage Tool
+*.dotCover
+
+# NCrunch
+*.ncrunch*
+.*crunch*.local.xml
+
+# Installshield output folder
+[Ee]xpress/
+
+# DocProject is a documentation generator add-in
+DocProject/buildhelp/
+DocProject/Help/*.HxT
+DocProject/Help/*.HxC
+DocProject/Help/*.hhc
+DocProject/Help/*.hhk
+DocProject/Help/*.hhp
+DocProject/Help/Html2
+DocProject/Help/html
+
+# Click-Once directory
+publish/
+
+# Publish Web Output
+*.Publish.xml
+
+# Windows Azure Build Output
+csx
+*.build.csdef
+
+# Windows Store app package directory
+AppPackages/
+
+# Others
+*.Cache
+ClientBin/
+[Ss]tyle[Cc]op.*
+~$*
+*~
+*.dbmdl
+*.[Pp]ublish.xml
+*.pfx
+*.publishsettings
+modulesbin/
+tempbin/
+
+# EPiServer Site file (VPP)
+AppData/
+
+# RIA/Silverlight projects
+Generated_Code/
+
+# Backup & report files from converting an old project file to a newer
+# Visual Studio version. Backup files are not needed, because we have git ;-)
+_UpgradeReport_Files/
+Backup*/
+UpgradeLog*.XML
+UpgradeLog*.htm
+
+# vim
+*.txt~
+*.swp
+*.swo
+
+# Temp files when opening LibreOffice on ubuntu
+.~lock.*
+
+# svn
+.svn
+
+# CVS - Source Control
+**/CVS/
+
+# Remainings from resolving conflicts in Source Control
+*.orig
+
+# SQL Server files
+**/App_Data/*.mdf
+**/App_Data/*.ldf
+**/App_Data/*.sdf
+
+
+#LightSwitch generated files
+GeneratedArtifacts/
+_Pvt_Extensions/
+ModelManifest.xml
+
+# =========================
+# Windows detritus
+# =========================
+
+# Windows image file caches
+Thumbs.db
+ehthumbs.db
+
+# Folder config file
+Desktop.ini
+
+# Recycle Bin used on file shares
+$RECYCLE.BIN/
+
+# OS generated files #
+Icon?
+
+# Mac desktop service store files
+.DS_Store
+
+# SASS Compiler cache
+.sass-cache
+
+# Visual Studio 2014 CTP
+**/*.sln.ide
+
+# Visual Studio temp something
+.vs/
+
+# dotnet stuff
+project.lock.json
+
+# VS 2015+
+*.vc.vc.opendb
+*.vc.db
+
+# Rider
+.idea/
+
+# Visual Studio Code
+.vscode/
+
+# Output folder used by Webpack or other FE stuff
+**/node_modules/*
+package-lock.json
+**/wwwroot/*
+
+# SpecFlow specific
+*.feature.cs
+*.feature.xlsx.*
+*.Specs_*.html
+
+# UWP Projects
+AppPackages/
+
+#####
+# End of core ignore list, below put you custom 'per project' settings (patterns or path)
+#####

Topic1_Arrays/Day2207/Exercise1.cs

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+//https://leetcode.com/problems/two-sum/submissions/1340665663/
+
+/*
++ To use Dictionary
+    + Key: current value
+    + Value: idx of its
++ When looping every single element, I need to get target minus current value to find
+whether that value exists in dictionary or not
+    + If it doesn't exist => add to dictionary
+    + If it exists => add to result array to return
+
+Space complexity: O(n)
+Time complexity: O(n)
+*/
+
+namespace Day2207
+{
+    public class Exercise1
+    {
+        public int[] TwoSum(int[] nums, int target)
+        {
+            Dictionary<int, int> myDict = new();
+
+            int[] result = new int[2];
+
+            for (int i = 0; i < nums.Length; ++i)
+            {
+                int calc = target - nums[i];
+                if (myDict.ContainsKey(calc))
+                {
+                    result[0] = myDict[calc];
+                    result[1] = i;
+                    break;
+
+                }
+                else
+                    myDict[nums[i]] = i;
+            }
+
+            return result;
+        }
+    }
+}

Topic1_Arrays/Day2207/Exercise2.cs

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+//https://leetcode.com/problems/number-of-islands/description/
+
+/*
++ To use recursion technique
++ I will loop every single element in 2d arrays
++ If current value is '1' => not visited => backtracking that position and plus 1 value of result
++ When backtracking current position, mark its neightbor values as '2' (islands but visited)
+
+Space complexity: O(n^2)
+Time complexity: O(1)
+*/
+
+namespace Day2207
+{
+    public class Exercise2
+    {
+        public int NumIslands(char[][] grid)
+        {
+            int row = grid.Length;
+            int col = grid[0].Length;
+
+            int result = 0;
+
+            for (int i = 0; i < row; ++i)
+            {
+                for (int j = 0; j < col; ++j)
+                {
+                    if (grid[i][j] == '1')
+                    {
+                        ++result;
+                        Backtrack(grid, i, j, row, col);
+                    }
+                }
+            }
+
+            return result;
+        }
+
+        private void Backtrack(char[][] grid, int i, int j, int m, int n)
+        {
+            if (i < 0 || i == m || j < 0 || j == n || grid[i][j] != '1')
+                return;
+
+            grid[i][j] = '2'; // visited
+
+            Backtrack(grid, i - 1, j, m, n);
+            Backtrack(grid, i, j - 1, m, n);
+            Backtrack(grid, i + 1, j, m, n);
+            Backtrack(grid, i, j + 1, m, n);
+        }
+    }
+}

Topic1_Arrays/Day2207/Exercise3.cs

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+//https://leetcode.com/problems/merge-sorted-array/
+
+/*
++ I will have 2 pointers at the end of every array
++ when comparing 2 current values in array, I need to move larger value into the end of array
++ Fill all remaining values of nums2 array into nums1 array
+
+Space complexity: O(m + n)
+Time complexity: O(1)
+*/
+
+namespace Day2207
+{
+    public class Exercise3
+    {
+        public void Merge(int[] nums1, int m, int[] nums2, int n)
+        {
+            int i = m - 1;
+            int j = n - 1;
+            int k = nums1.Length - 1;
+
+            while (i >= 0 && j >= 0)
+            {
+                if (nums1[i] >= nums2[j])
+                    nums1[k--] = nums1[i--];
+                else
+                    nums1[k--] = nums2[j--];
+            }
+
+
+            //fill all remaining elements in nums2 array into nums1 array
+            while (j >= 0)
+                nums1[k--] = nums2[j--];
+        }
+    }
+}