Code/README fixes for the "Palindrome Check".

trekhleb · trekhleb · commit 90addf9b1827 · 2022-01-23T21:47:57.000+01:00
diff --git a/README.md b/README.md
@@ -102,7 +102,7 @@ a set of rules that precisely define a sequence of operations.
   * `A` [Combination Sum](src/algorithms/sets/combination-sum) - find all combinations that form specific sum
 * **Strings**
   * `B` [Hamming Distance](src/algorithms/string/hamming-distance) - number of positions at which the symbols are different
-  * `B` [Palindrome Check](src/algorithms/string/palindrome-check) - is the string the same in reverse
+  * `B` [Palindrome](src/algorithms/string/palindrome) - check if the string is the same in reverse
   * `A` [Levenshtein Distance](src/algorithms/string/levenshtein-distance) - minimum edit distance between two sequences
   * `A` [Knuth–Morris–Pratt Algorithm](src/algorithms/string/knuth-morris-pratt) (KMP Algorithm) - substring search (pattern matching)
   * `A` [Z Algorithm](src/algorithms/string/z-algorithm) - substring search (pattern matching)
diff --git a/src/algorithms/string/palindrome-check/README.md b/src/algorithms/string/palindrome-check/README.md
diff --git a/src/algorithms/string/palindrome-check/__test__/palindromeCheck.test.js b/src/algorithms/string/palindrome-check/__test__/palindromeCheck.test.js
diff --git a/src/algorithms/string/palindrome/README.md b/src/algorithms/string/palindrome/README.md
@@ -0,0 +1,29 @@
+# Palindrome Check
+
+A [Palindrome](https://en.wikipedia.org/wiki/Palindrome) is a string that reads the same forwards and backwards.
+This means that the second half of the string is the reverse of the
+first half.
+
+## Examples
+
+The following are palindromes (thus would return `TRUE`):
+
+```
+- "a"
+- "pop"     ->  p + o + p
+- "deed"    ->  de + ed
+- "kayak"   ->  ka + y + ak
+- "racecar" ->  rac + e + car
+```
+
+The following are NOT palindromes (thus would return `FALSE`):
+
+```
+- "rad"
+- "dodo"
+- "polo"
+```
+
+## References
+
+- [GeeksForGeeks - Check if a number is Palindrome](https://www.geeksforgeeks.org/check-if-a-number-is-palindrome/)
diff --git a/src/algorithms/string/palindrome/__test__/isPalindrome.test.js b/src/algorithms/string/palindrome/__test__/isPalindrome.test.js
@@ -0,0 +1,15 @@
+import isPalindrome from '../isPalindrome';
+
+describe('palindromeCheck', () => {
+  it('should return whether or not the string is a palindrome', () => {
+    expect(isPalindrome('a')).toBe(true);
+    expect(isPalindrome('pop')).toBe(true);
+    expect(isPalindrome('deed')).toBe(true);
+    expect(isPalindrome('kayak')).toBe(true);
+    expect(isPalindrome('racecar')).toBe(true);
+
+    expect(isPalindrome('rad')).toBe(false);
+    expect(isPalindrome('dodo')).toBe(false);
+    expect(isPalindrome('polo')).toBe(false);
+  });
+});
diff --git a/src/algorithms/string/palindrome/isPalindrome.js b/src/algorithms/string/palindrome/isPalindrome.js
@@ -3,15 +3,17 @@
  * @return {boolean}
  */
 
-export default function palindromeCheck(string) {
+export default function isPalindrome(string) {
   let left = 0;
   let right = string.length - 1;
+
   while (left < right) {
     if (string[left] !== string[right]) {
       return false;
     }
     left += 1;
     right -= 1;
   }
+
   return true;
 }

Original file line number	Diff line number	Diff line change
`@@ -3,15 +3,17 @@`
`3`	`3`	`* @return {boolean}`
`4`	`4`	`*/`
`5`	`5`
`6`		`-export default function palindromeCheck(string) {`
	`6`	`+export default function isPalindrome(string) {`
`7`	`7`	`let left = 0;`
`8`	`8`	`let right = string.length - 1;`
	`9`	`+`
`9`	`10`	`while (left < right) {`
`10`	`11`	`if (string[left] !== string[right]) {`
`11`	`12`	`return false;`
`12`	`13`	`}`
`13`	`14`	`left += 1;`
`14`	`15`	`right -= 1;`
`15`	`16`	`}`
	`17`	`+`
`16`	`18`	`return true;`
`17`	`19`	`}`