re-write palindrome algorithmn

Quadriphobs1 · Quadriphobs1 · commit 55fe590479e3 · 2019-10-01T13:44:07.000+01:00
diff --git a/palindrome/palindrome.js b/palindrome/palindrome.js
@@ -0,0 +1,27 @@
+function isPalindromeRecursive(chars, s, e) {
+  if (s === e) {
+    return true;
+  }
+  
+  if (chars[s] !== chars[e]) {
+    return false;
+  }
+
+  if (s < e + 1) {
+    return isPalindromeRecursive(chars, s + 1, e - 1)
+  }
+
+  return true;
+}
+
+function isPalindrome(s) {
+  // convert the input to string
+  const chars = String(s);
+  const len = chars.length
+  if (len <= 1) {
+    return true
+  }
+  return isPalindromeRecursive(chars, 0, len - 1);
+}
+
+module.exports = isPalindrome;
diff --git a/palindrome/palindrome.test.js b/palindrome/palindrome.test.js
@@ -0,0 +1,22 @@
+const isPalindrome = require('./palindrome');
+
+describe('isPalindrome()', () => {
+  it('should return true for single number', () => {
+    expect(isPalindrome(1)).toBeTruthy();
+  })
+
+  it('should return true for valid number "121"', () => {
+    expect(isPalindrome(121)).toBeTruthy();
+  })
+
+  it('should return true for same number 111', () => {
+    expect(isPalindrome(111)).toBeTruthy();
+  })
+  it('should return false for invalid number', () => {
+    expect(isPalindrome(123)).toBeFalsy();
+  })
+
+  it('should return true for long value', () => {
+    expect(isPalindrome(123321123321)).toBeTruthy();
+  })
+})
diff --git a/src/palindrome.js b/src/palindrome.js
