Abbreviation (#1547)

* Abbreviation

* Updates from code review

Dynamic-Programming/Abbreviation.js

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+/**
+ * @description
+ * Given two strings, `source` and `target`, determine if it's possible to make `source` equal
+ * to `target` You can perform the following operations on the string `source`:
+ * 1. Capitalize zero or more of `source`'s lowercase letters.
+ * 2. Delete all the remaining lowercase letters in `source`.
+ *
+ * Time Complexity: (O(|source|*|target|)) where `|source|` => length of string `source`
+ *
+ * @param {String} source - The string to be transformed.
+ * @param {String} target - The string we want to transform `source` into.
+ * @returns {Boolean} - Whether the transformation is possible.
+ * @see https://www.hackerrank.com/challenges/abbr/problem - Related problem on HackerRank.
+ */
+export const isAbbreviation = (source, target) => {
+  const sourceLength = source.length
+  const targetLength = target.length
+
+  // Initialize a table to keep track of possible abbreviations
+  let canAbbreviate = Array.from({ length: sourceLength + 1 }, () =>
+    Array(targetLength + 1).fill(false)
+  )
+  // Empty strings are trivially abbreviatable
+  canAbbreviate[0][0] = true
+
+  for (let sourceIndex = 0; sourceIndex < sourceLength; sourceIndex++) {
+    for (let targetIndex = 0; targetIndex <= targetLength; targetIndex++) {
+      if (canAbbreviate[sourceIndex][targetIndex]) {
+        // If characters at the current position are equal, move to the next position in both strings.
+        if (
+          targetIndex < targetLength &&
+          source[sourceIndex].toUpperCase() === target[targetIndex]
+        ) {
+          canAbbreviate[sourceIndex + 1][targetIndex + 1] = true
+        }
+        // If the current character in `source` is lowercase, explore two possibilities:
+        // a) Capitalize it (which is akin to "using" it in `source` to match `target`), or
+        // b) Skip it (effectively deleting it from `source`).
+        if (source[sourceIndex] === source[sourceIndex].toLowerCase()) {
+          canAbbreviate[sourceIndex + 1][targetIndex] = true
+        }
+      }
+    }
+  }
+
+  return canAbbreviate[sourceLength][targetLength]
+}

Dynamic-Programming/tests/Abbreviation.test.js

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+import { isAbbreviation } from '../Abbreviation.js'
+
+const expectPositive = (word, abbr) =>
+  expect(isAbbreviation(word, abbr)).toBe(true)
+const expectNegative = (word, abbr) =>
+  expect(isAbbreviation(word, abbr)).toBe(false)
+
+describe('Abbreviation - Positive Tests', () => {
+  test('it should correctly abbreviate or transform the source string to match the target string', () => {
+    expectPositive('', '')
+    expectPositive('a', '')
+    expectPositive('a', 'A')
+    expectPositive('abcDE', 'ABCDE')
+    expectPositive('ABcDE', 'ABCDE')
+    expectPositive('abcde', 'ABCDE')
+    expectPositive('abcde', 'ABC')
+    expectPositive('abcXYdefghijKLmnopqrs', 'XYKL')
+    expectPositive('abc123', 'ABC')
+    expectPositive('abc123', 'ABC123')
+    expectPositive('abc!@#def', 'ABC')
+  })
+})
+
+describe('Abbreviation - Negative Tests', () => {
+  test('it should fail to abbreviate or transform the source string when it is not possible to match the target string', () => {
+    expectNegative('', 'A')
+    expectNegative('a', 'ABC')
+    expectNegative('aBcXYdefghijKLmnOpqrs', 'XYKLOP')
+  })
+})