Day8-9

20. Valid Parentheses/20. Valid Parentheses.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net6.0</TargetFramework>
+    <RootNamespace>_20._Valid_Parentheses</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

20. Valid Parentheses/Program.cs

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+namespace _20._Valid_Parentheses;
+
+internal class Program
+{
+    static void Main(string[] args)
+    {
+        Console.WriteLine(new Solution().IsValid("([)]"));
+    }
+}

20. Valid Parentheses/Solution.cs

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+using System.Text;
+
+namespace _20._Valid_Parentheses;
+
+public class Solution
+{
+    public bool IsValid(string s)
+    {
+        StringBuilder sb = new StringBuilder(s);
+        if (sb.Length == 0)
+            return true;
+        if (sb.Length % 2 == 1)
+            return false;
+        while(sb.Length > 0)
+        {
+            char ch = sb[0];
+            if ("({[".Contains(ch) == false)
+                return false;
+            char need = ch switch
+            {
+                '(' => ')',
+                '{' => '}',
+                '[' => ']',
+                _ => '\0'
+            };
+            int count1 = 0;// ()
+            int count2 = 0;// {}
+            int count3 = 0;// []
+            bool succes = false;
+            for(int i = 1; i < sb.Length; i++)
+            {
+                char c = sb[i];
+                if (count1 == 0 && count2 == 0 && count3 == 0 && c == need)
+                {
+                    sb.Remove(i, 1).Remove(0, 1);
+                    succes = true;
+                    break;
+                }
+                switch (c)
+                {
+                    case '(':
+                        count1++;
+                        break;
+                    case ')':
+                        count1--;
+                        break;
+
+                    case '{':
+                        count2++;
+                        break;
+                    case '}':
+                        count2--;
+                        break;
+
+                    case '[':
+                        count3++;
+                        break;
+                    case ']':
+                        count3--;
+                        break;
+                }
+            }
+            if(succes == false)
+                return false;
+        }
+        return true;
+    }
+}