[Hacker Rank] Interview Preparation Kit: Stacks and Queues: Balanced Brackets. Solved ✅.

Author: Gonzalo Diaz

docs/hackerrank/interview_preparation_kit/stacks_and_queues/balanced-brackets.md

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+# [Balanced Brackets](https://www.hackerrank.com/challenges/balanced-brackets/)
+
+Given a string containing three types of brackets, determine if it is balanced.
+
+- Difficulty:  `#medium`
+- Category: `#ProblemSolvingIntermediate` `#stacksAndQueues`
+
+A bracket is considered to be any one of the following characters:
+(, ), {, }, [, or ].
+
+Two brackets are considered to be a matched pair if the an opening bracket
+(i.e., (, [, or {) occurs to the left of a closing bracket (i.e., ), ], or })
+of the exact same type. There are three types of matched pairs of brackets:
+[], {}, and ().
+
+A matching pair of brackets is not balanced if the set of brackets it encloses
+are not matched. For example, {[(])} is not balanced because the contents
+in between { and } are not balanced.
+The pair of square brackets encloses a single, unbalanced opening bracket,
+(, and the pair of parentheses encloses a single,
+unbalanced closing square bracket, ].
+
+By this logic, we say a sequence of brackets is balanced if
+the following conditions are met:
+
+- It contains no unmatched brackets.
+- The subset of brackets enclosed within the confines of a matched
+pair of brackets is also a matched pair of brackets.
+
+Given `n` strings of brackets, determine whether each sequence
+of brackets is balanced. If a string is balanced, return `YES`.
+Otherwise, return `NO`.
+
+## Function Description
+
+Complete the function isBalanced in the editor below.
+
+isBalanced has the following parameter(s):
+
+- `string s`: a string of brackets
+
+## Returns
+
+- `string`: either `YES` or `NO`
+
+## Input Format
+
+The first line contains a single integer `n`, the number of strings.
+Each of the next `n` lines contains a single string `s`, a sequence of brackets.
+
+## Constraints
+
+- $ 1 \leq n \leq 10^3 $
+- $ 1 \leq \lvert s \rvert \leq 10^3 $, where $ \lvert s \rvert  $ is the length
+of the sequence.
+- All chracters in the sequences ∈ { `{`, `}`, `(`, `)`, `[`, `]` }.
+
+## Output Format
+
+For each string, return YES or NO.
+
+## Sample Input
+
+```text
+STDIN           Function
+-----           --------
+3               n = 3
+{[()]}          first s = '{[()]}'
+{[(])}          second s = '{[(])}'
+{{[[(())]]}}    third s ='{{[[(())]]}}'
+```
+
+## Sample Output
+
+```text
+YES
+NO
+YES
+```
+
+## Explanation
+
+The string {[()]} meets both criteria for being a balanced string.
+The string {[(])} is not balanced because the brackets enclosed
+by the matched pair { and } are not balanced: [(]).
+The string {{[[(())]]}} meets both criteria for being a balanced string.

src/hackerrank/interview_preparation_kit/stacks_and_queues/balanced_brackets.test.ts

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+import { describe, expect, it } from '@jest/globals';
+
+import { isBalanced } from './balanced_brackets';
+import TEST_CASES from './balanced_brackets.testcases.json';
+
+describe('isBalanced', () => {
+  it('isBalanced test cases', () => {
+    expect.assertions(8);
+
+    const __YES__ = 'YES';
+
+    TEST_CASES.forEach((testSet) => {
+      testSet?.tests.forEach((test) => {
+        const result = isBalanced(test.input) === __YES__;
+
+        expect(result).toStrictEqual(test.expected);
+      });
+    });
+  });
+});

src/hackerrank/interview_preparation_kit/stacks_and_queues/balanced_brackets.testcases.json

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+[
+  {
+    "title": "Sample Test Case 0",
+    "tests":
+    [
+      {
+        "input": "{[()]}",
+        "expected": true
+      },
+      {
+        "input": "{[(])}",
+        "expected": false
+      },
+      {
+        "input": "{{[[(())]]}}",
+        "expected": true
+      }
+    ]
+  },
+  {
+    "title": "Sample Test Case 1",
+    "tests":
+    [
+      {
+        "input": "{{([])}}",
+        "expected": true
+      },
+      {
+        "input": "{{)[](}}",
+        "expected": false
+      }
+    ]
+  },
+  {
+    "title": "Sample Test Case 1",
+    "tests":
+    [
+      {
+        "input": "{(([])[])[]}",
+        "expected": true
+      },
+      {
+        "input": "{(([])[])[]]}",
+        "expected": false
+      },
+      {
+        "input": "{(([])[])[]}[]",
+        "expected": true
+      }
+    ]
+  }
+]

src/hackerrank/interview_preparation_kit/stacks_and_queues/balanced_brackets.ts

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+/**
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/stacks_and_queues/balanced-brackets.md]]
+ */
+
+const __YES__ = 'YES';
+const __NO__ = 'NO';
+
+export function isBalancedCompute(s: string): boolean {
+  const pairs: Record<string, string> = { '{': '}', '(': ')', '[': ']' };
+  const brackets: string[] = [];
+
+  for (const letter of s.split('')) {
+    if (letter in pairs) {
+      brackets.push(letter);
+    } else if (
+      brackets.length > 0 &&
+      pairs[brackets[brackets.length - 1]] === letter
+    ) {
+      brackets.pop();
+    } else {
+      return false;
+    }
+
+    console.debug(letter);
+  }
+
+  return brackets.length <= 0;
+}
+
+export function isBalanced(s: string): string {
+  return isBalancedCompute(s) ? __YES__ : __NO__;
+}
+
+export default { isBalanced };