add solution for valid parenthese

readme.md

@@ -1,4 +1,4 @@
-## Algorithms (18/ 167)
+## Algorithms (19/ 167)
 
 | Name                                                      | Tags                    | Solution                                                                |
 | --------------------------------------------------------- | ----------------------- | ----------------------------------------------------------------------- |
@@ -32,7 +32,7 @@
 | 3Sum                                                      | `Two Pointers`          |                                                                         |
 | Container With Most Water                                 | `Two Pointers`          |                                                                         |
 | Trapping Rain Water                                       | `Two Pointers`          |                                                                         |
-| Valid Parentheses                                         | `Stack`                 |                                                                         |
+| Valid Parentheses                                         | `Stack`                 | [Typescript]('./src/algorithms/stack/valid-parentheses')                |
 | Min Stack                                                 | `Stack`                 |                                                                         |
 | Evaluate Reverse Polish Notation                          | `Stack`                 |                                                                         |
 | Generate Parentheses                                      | `Stack`                 |                                                                         |

src/algorithms/stack/valid-parentheses/valid-parentheses.spec.ts

@@ -0,0 +1,14 @@
+import { isValid } from './valid-parentheses'
+
+describe('Valid parentheses', () => {
+  it('is valid', () => {
+    expect(isValid('()')).toBe(true)
+    expect(isValid('()[]{}')).toBe(true)
+    expect(isValid('{[]}')).toBe(true)
+  })
+
+  it('is invalid', () => {
+    expect(isValid('(]')).toBe(false)
+    expect(isValid('([)]')).toBe(false)
+  })
+})

src/algorithms/stack/valid-parentheses/valid-parentheses.ts

@@ -0,0 +1,36 @@
+/**
+ * Valid Parentheses
+ * Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
+
+    An input string is valid if:
+
+    1. Open brackets must be closed by the same type of brackets.
+    2. Open brackets must be closed in the correct order.
+    3. Every close bracket has a corresponding open bracket of the same type.
+
+    Example 1:
+    Input: s = "()"
+    Output: true
+
+    Example 2:
+    Input: s = "()[]{}"
+    Output: true
+ *
+ */
+export function isValid(s: string): boolean {
+  const stack: string[] = []
+
+  for (const char of s) {
+    if (char === '(') {
+      stack.push(')')
+    } else if (char === '[') {
+      stack.push(']')
+    } else if (char === '{') {
+      stack.push('}')
+    } else if (stack.pop() !== char) {
+      return false
+    }
+  }
+
+  return stack.length === 0
+}