Add matching-brackets exercise

config.json

@@ -728,6 +728,14 @@
         "practices": [],
         "prerequisites": [],
         "difficulty": 1
+      },
+      {
+        "slug": "matching-brackets",
+        "name": "Matching Brackets",
+        "uuid": "8e78cebc-5e33-4670-bc87-f481bdd0bf49",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 3
       }
     ]
   },

exercises/practice/matching-brackets/.docs/instructions.md

@@ -0,0 +1,5 @@
+# Instructions
+
+Given a string containing brackets `[]`, braces `{}`, parentheses `()`, or any combination thereof, verify that any and all pairs are matched and nested correctly.
+Any other characters should be ignored.
+For example, `"{what is (42)}?"` is balanced and `"[text}"` is not.

exercises/practice/matching-brackets/.docs/introduction.md

@@ -0,0 +1,8 @@
+# Introduction
+
+You're given the opportunity to write software for the Bracketeer™, an ancient but powerful mainframe.
+The software that runs on it is written in a proprietary language.
+Much of its syntax is familiar, but you notice _lots_ of brackets, braces and parentheses.
+Despite the Bracketeer™ being powerful, it lacks flexibility.
+If the source code has any unbalanced brackets, braces or parentheses, the Bracketeer™ crashes and must be rebooted.
+To avoid such a scenario, you start writing code that can verify that brackets, braces, and parentheses are balanced before attempting to run it on the Bracketeer™.

exercises/practice/matching-brackets/.meta/config.json

@@ -0,0 +1,18 @@
+{
+  "authors": [
+    "erikschierboom"
+  ],
+  "files": {
+    "solution": [
+      "matching-brackets.R"
+    ],
+    "test": [
+      "test_matching-brackets.R"
+    ],
+    "example": [
+      ".meta/example.R"
+    ]
+  },
+  "blurb": "Make sure the brackets and braces all match.",
+  "source": "Ginna Baker"
+}

exercises/practice/matching-brackets/.meta/example.R

@@ -0,0 +1,18 @@
+is_paired <- function(input) {
+  mapping <- list("{" = "}", "[" = "]", "(" = ")")
+  expected <- list()
+
+  for (c in strsplit(input, "") |> unlist()) {
+    if (hasName(mapping, c)) {
+      expected <- append(expected, mapping[c])
+    } else if (c %in% mapping) {
+      if (length(expected) == 0 || c != tail(expected, n = 1)) {
+        return(FALSE)
+      }
+
+      expected <- expected[-length(expected)]
+    }
+  }
+
+  length(expected) == 0
+}

exercises/practice/matching-brackets/.meta/tests.toml

@@ -0,0 +1,70 @@
+# This is an auto-generated file.
+#
+# Regenerating this file via `configlet sync` will:
+# - Recreate every `description` key/value pair
+# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
+# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
+# - Preserve any other key/value pair
+#
+# As user-added comments (using the # character) will be removed when this file
+# is regenerated, comments can be added via a `comment` key.
+
+[81ec11da-38dd-442a-bcf9-3de7754609a5]
+description = "paired square brackets"
+
+[287f0167-ac60-4b64-8452-a0aa8f4e5238]
+description = "empty string"
+
+[6c3615a3-df01-4130-a731-8ef5f5d78dac]
+description = "unpaired brackets"
+
+[9d414171-9b98-4cac-a4e5-941039a97a77]
+description = "wrong ordered brackets"
+
+[f0f97c94-a149-4736-bc61-f2c5148ffb85]
+description = "wrong closing bracket"
+
+[754468e0-4696-4582-a30e-534d47d69756]
+description = "paired with whitespace"
+
+[ba84f6ee-8164-434a-9c3e-b02c7f8e8545]
+description = "partially paired brackets"
+
+[3c86c897-5ff3-4a2b-ad9b-47ac3a30651d]
+description = "simple nested brackets"
+
+[2d137f2c-a19e-4993-9830-83967a2d4726]
+description = "several paired brackets"
+
+[2e1f7b56-c137-4c92-9781-958638885a44]
+description = "paired and nested brackets"
+
+[84f6233b-e0f7-4077-8966-8085d295c19b]
+description = "unopened closing brackets"
+
+[9b18c67d-7595-4982-b2c5-4cb949745d49]
+description = "unpaired and nested brackets"
+
+[a0205e34-c2ac-49e6-a88a-899508d7d68e]
+description = "paired and wrong nested brackets"
+
+[1d5c093f-fc84-41fb-8c2a-e052f9581602]
+description = "paired and wrong nested brackets but innermost are correct"
+
+[ef47c21b-bcfd-4998-844c-7ad5daad90a8]
+description = "paired and incomplete brackets"
+
+[a4675a40-a8be-4fc2-bc47-2a282ce6edbe]
+description = "too many closing brackets"
+
+[a345a753-d889-4b7e-99ae-34ac85910d1a]
+description = "early unexpected brackets"
+
+[21f81d61-1608-465a-b850-baa44c5def83]
+description = "early mismatched brackets"
+
+[99255f93-261b-4435-a352-02bdecc9bdf2]
+description = "math expression"
+
+[8e357d79-f302-469a-8515-2561877256a1]
+description = "complex latex expression"

exercises/practice/matching-brackets/matching-brackets.R

@@ -0,0 +1,3 @@
+is_paired <- function(input) {
+
+}

exercises/practice/matching-brackets/test_matching-brackets.R

@@ -0,0 +1,84 @@
+source("./matching-brackets.R")
+library(testthat)
+
+test_that("Paired square brackets", {
+  expect_equal(is_paired("[]"), TRUE)
+})
+
+test_that("Empty string", {
+  expect_equal(is_paired(""), TRUE)
+})
+
+test_that("Unpaired brackets", {
+  expect_equal(is_paired("[["), FALSE)
+})
+
+test_that("Wrong ordered brackets", {
+  expect_equal(is_paired("}{"), FALSE)
+})
+
+test_that("Wrong closing bracket", {
+  expect_equal(is_paired("{]"), FALSE)
+})
+
+test_that("Paired with whitespace", {
+  expect_equal(is_paired("{ }"), TRUE)
+})
+
+test_that("Partially paired brackets", {
+  expect_equal(is_paired("{[])"), FALSE)
+})
+
+test_that("Simple nested brackets", {
+  expect_equal(is_paired("{[]}"), TRUE)
+})
+
+test_that("Several paired brackets", {
+  expect_equal(is_paired("{}[]"), TRUE)
+})
+
+test_that("Paired and nested brackets", {
+  expect_equal(is_paired("([{}({}[])])"), TRUE)
+})
+
+test_that("Unopened closing brackets", {
+  expect_equal(is_paired("{[)][]}"), FALSE)
+})
+
+test_that("Unpaired and nested brackets", {
+  expect_equal(is_paired("([{])"), FALSE)
+})
+
+test_that("Paired and wrong nested brackets", {
+  expect_equal(is_paired("[({]})"), FALSE)
+})
+
+test_that("Paired and wrong nested brackets but innermost are correct", {
+  expect_equal(is_paired("[({}])"), FALSE)
+})
+
+test_that("Paired and incomplete brackets", {
+  expect_equal(is_paired("{}["), FALSE)
+})
+
+test_that("Too many closing brackets", {
+  expect_equal(is_paired("[]]"), FALSE)
+})
+
+test_that("Early unexpected brackets", {
+  expect_equal(is_paired(")()"), FALSE)
+})
+
+test_that("Early mismatched brackets", {
+  expect_equal(is_paired("{)()"), FALSE)
+})
+
+test_that("Math expression", {
+  input <- "(((185 + 223.85) * 15) - 543)/2"
+  expect_equal(is_paired(input), TRUE)
+})
+
+test_that("Complex latex expression", {
+  input <- "\\left(\\begin{array}{cc} \\frac{1}{3} & x\\ \\mathrm{e}^{x} &... x^2 \\end{array}\\right)" # nolint
+  expect_equal(is_paired(input), TRUE)
+})