Valid Parentheses - String - Easy - LeetCode

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

Open brackets must be closed by the same type of brackets.

Open brackets must be closed in the correct order.

Note that an empty string is also considered valid.

Example 1:

Input: "()"

Output: true

Example 2:

Input: "()[]{}"

Output: true

Example 3:

Input: "(]"

Output: false

Example 4:

Input: "([)]"

Output: false

Example 5:

Input: "{[]}"

Output: true

Solution:

using System;
using System.Collections.Generic;
using System.Text;

namespace LeetCode.AskGif.Easy.String
{
 public class IsValidSoln
 {
 public bool IsValid(string s)
 {
 var stack = new Stack<char>();
 var map = new Dictionary<char, char>();
 map.Add('(', ')');
 map.Add('{', '}');
 map.Add('[', ']');

 for (int i = 0; i < s.Length; i++)
 {
 if (map.ContainsKey(s[i]))
 {
 stack.Push(s[i]);
 }
 else
 {
 if(stack.Count == 0)
 {
 return false;
 }

 var ch = stack.Pop();
 if(map[ch] != s[i])
 {
 return false;
 }
 }
 }

 if(stack.Count > 0)
 {
 return false;
 }

 return true;
 }
 }
}

Time Complexity: O(n)

Space Complexity: O(n)

Unit Tests:

using LeetCode.AskGif.Easy.String;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using System.Collections.Generic;
using System.Text;

namespace CodingUnitTest.Easy.String
{
 [TestClass]
 public class IsValidSolnTests
 {
 [TestMethod]
 public void IsValidSoln_First()
 {
 var input = "()";
 var output = true;
 var res = new IsValidSoln().IsValid(input);

 Assert.AreEqual(res, output);
 }

 [TestMethod]
 public void IsValidSoln_Second()
 {
 var input = "()[]{}";
 var output = true;
 var res = new IsValidSoln().IsValid(input);

 Assert.AreEqual(res, output);
 }

 [TestMethod]
 public void IsValidSoln_Third()
 {
 var input = "(]";
 var output = false;
 var res = new IsValidSoln().IsValid(input);

 Assert.AreEqual(res, output);
 }

 [TestMethod]
 public void IsValidSoln_Fourth()
 {
 var input = "([)]";
 var output = false;
 var res = new IsValidSoln().IsValid(input);

 Assert.AreEqual(res, output);
 }

 [TestMethod]
 public void IsValidSoln_Fifth()
 {
 var input = "{[]}";
 var output = true;
 var res = new IsValidSoln().IsValid(input);

 Assert.AreEqual(res, output);
 }
 }
}