feat: solve leetcode 0020

Author: JCPedroza

src/leet-code/0020-valid-parentheses/valid-parenth-stack.js

@@ -0,0 +1,57 @@
+const parens = new Map([
+  ['(', ')'],
+  ['[', ']'],
+  ['{', '}']
+])
+
+/**
+ * Unboxes a string option into a string.
+ *
+ * @param {string | undefined} str String option to be unboxed.
+ * @returns {string} Unboxed string.
+ */
+const unboxOption = (str) => {
+  if (str === undefined) {
+    throw new Error('string is undefined')
+  }
+
+  return str
+}
+
+/**
+ * Validates whether a string contains valid parentheses. Uses a stack.
+ *
+ * Time complexity: O(n)
+ * Space complexity: O(n)
+ *
+ * @param {string} str String to be validated
+ * @returns Whether the string contains valid parentheses.
+ */
+const hasValidParentheses = (str) => {
+  // Empty string is valid
+  if (str.length === 0) return true
+
+  // String of odd length can't be valid
+  if (str.length % 2 !== 0) return false
+
+  /** @type {string[]} */
+  const stack = []
+
+  for (let idx = 0; idx < str.length; idx++) {
+    const currentChar = str[idx]
+
+    if (parens.has(currentChar)) {
+      stack.push(unboxOption(parens.get(currentChar)))
+    } else if (stack.pop() !== currentChar) {
+      return false
+    }
+  }
+
+  // If the stack is empty, all parentheses have been closed.
+  return stack.length === 0
+}
+
+module.exports = {
+  fun: hasValidParentheses,
+  id: 'stack'
+}

src/leet-code/0020-valid-parentheses/valid-parenth.repo.js

@@ -0,0 +1,7 @@
+const isParenthStack = require('./valid-parenth-stack')
+
+const solutions = [
+  isParenthStack
+]
+
+module.exports = solutions

src/leet-code/0020-valid-parentheses/valid-parenth.test.js

@@ -0,0 +1,41 @@
+const assert = require('node:assert/strict')
+const { describe, it } = require('node:test')
+
+const solutions = require('./valid-parenth.repo')
+
+for (const { fun, id } of solutions) {
+  describe(`LeetCode 0020 'Valid Parentheses' solution '${id}'`, () => {
+    it('returns true for empty string', () => {
+      assert.equal(fun(''), true)
+    })
+
+    it('returns false for string of size 1', () => {
+      assert.equal(fun('['), false)
+    })
+
+    it('identifies valid strings of length 2', () => {
+      assert.equal(fun('()'), true)
+      assert.equal(fun('[]'), true)
+      assert.equal(fun('[]'), true)
+    })
+
+    it('identifies invalid strings of length 2', () => {
+      assert.equal(fun('(('), false)
+      assert.equal(fun('(]'), false)
+      assert.equal(fun(')('), false)
+    })
+
+    it('returns false for strings of odd length', () => {
+      assert.equal(fun('()('), false)
+      assert.equal(fun('[)]()'), false)
+      assert.equal(fun('([[()]]'), false)
+    })
+
+    it('identifies valid string of length 4', () => {
+      assert.equal(fun('(())'), true)
+      assert.equal(fun('({})'), true)
+      assert.equal(fun('()[]'), true)
+      assert.equal(fun('()()'), true)
+    })
+  })
+}