add: reverse integer

LeetcodeProblems/Algorithms/Reverse_Integer.js

@@ -0,0 +1,46 @@
+/**
+Reverse Integer
+https://leetcode.com/problems/reverse-integer/
+
+Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range [-231, 231 - 1], then return 0.
+
+Assume the environment does not allow you to store 64-bit integers (signed or unsigned).
+
+Example 1:
+Input: x = 123
+Output: 321
+
+Example 2:
+Input: x = -123
+Output: -321
+
+Example 3:
+Input: x = 120
+Output: 21
+
+ */
+
+/**
+ * @param {number} x
+ * @return {number}
+ */
+var reverseInteger = function(x) {
+  const sign = x >= 0 ? 1 : -1;
+
+  let baseNum = sign * x;
+  let builder = 0;
+
+  while (baseNum > 0) {
+    const digit = baseNum % 10;
+    builder = builder * 10 + digit;
+    baseNum = (baseNum / 10) | 0;
+  }
+
+  builder *= sign;
+
+  const isWithinRange = (builder >= -Math.pow(2, 31) && builder <= Math.pow(2, 31) - 1);
+
+  return isWithinRange ? builder : 0;
+};
+
+module.exports.reverseInteger = reverseInteger;

LeetcodeProblemsTests/Algorithms/Reverse_Integer_Test.js

@@ -0,0 +1,11 @@
+const assert = require('assert');
+const reverseInteger = require('../../LeetcodeProblems/Algorithms/Reverse_Integer').reverseInteger;
+
+var test = function() {
+  assert.equal(reverseInteger(123), 321);
+  assert.equal(reverseInteger(-123), -321);
+  assert.equal(reverseInteger(120), 21);
+}
+
+
+module.exports.test = test;

README.md

@@ -62,8 +62,9 @@ To run a specific problem in your console run  `node <problem_file_path>` (e.g.
 | [Construct Binary Tree from Preorder and Inorder Traversal ](/LeetcodeProblems/Algorithms/Construct_Binary_Tree_from_Preorder_and_Inorder_Traversal.js)   | Medium | https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/ | 
 | [Lowest Common Ancestor of a Binary Tree ](/LeetcodeProblems/Algorithms/Lowest_Common_Ancestor_of_a_Binary_Tree.js) | Medium | https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/ |
 | [Maximum Sum of an Hourglass](/LeetcodeProblems/Algorithms/Maximise_Hour_Glass_Sum.js)                          | Medium | https://leetcode.com/problems/maximum-sum-of-an-hourglass/ |
-| [Time Needed to Rearrange a Binary String](/LeetcodeProblems/Algorithms/Time_Needed_Rearrange_Binary_String.js)| Medium | https://leetcode.com/problems/time-needed-to-rearrange-a-binary-string/ |
-| [Find Subarrays With Equal Sum ](/LeetcodeProblems/Algorithms/Find_Subarrays_With_Equal_Sums.js)                                                                   | Medium | https://leetcode.com/problems/find-subarrays-with-equal-sum/ | 
+| [Reverse Integer](/LeetcodeProblems/Algorithms/Reverse_Integer.js)                                              | Medium | https://leetcode.com/problems/reverse-integer/ |
+| [Time Needed to Rearrange a Binary String](/LeetcodeProblems/Algorithms/Time_Needed_Rearrange_Binary_String.js) | Medium | https://leetcode.com/problems/time-needed-to-rearrange-a-binary-string/ |
+| [Find Subarrays With Equal Sum ](/LeetcodeProblems/Algorithms/Find_Subarrays_With_Equal_Sums.js)                | Medium | https://leetcode.com/problems/find-subarrays-with-equal-sum/ | 
 | [Flood Fill ](/LeetcodeProblems/Algorithms/Flood_Fill.js)                                                       | Easy   | https://leetcode.com/problems/flood-fill/ |
 | [Implement stack using queues ](/LeetcodeProblems/Algorithms/Implement_stack_using_queues.js)                   | Easy   | https://leetcode.com/problems/implement-stack-using-queues/ |
 | [Number of Segments in a String ](/LeetcodeProblems/Algorithms/Number_of_Segments_in_a_String.js)               | Easy   | https://leetcode.com/problems/number-of-segments-in-a-string/ |