--update: 32-bit signed int reversal

Author: ashokdey

src/_Problems_/reverse-number/index.js

@@ -15,6 +15,47 @@ function reverseNumber(num) {
   return reverse * Math.sign(num);
 }
 
+/**
+ * 
+ * Given a 32-bit signed integer, reverse digits of an integer.
+
+  Example 1:
+
+  Input: 123
+  Output: 321
+  Example 2:
+
+  Input: -123
+  Output: -321
+  Example 3:
+
+  Input: 1534236469
+  Output: 0 // overflows
+  Note:
+  Assume we are dealing with an environment which could only 
+  store integers within the 32-bit signed integer range: [−2^31,  2^31 − 1]. 
+  For the purpose of this problem, assume that your function returns 0 when the reversed integer overflows.
+ */
+
+function reverse32BitInt(x) {
+  let isNegetive = 0;
+  if (x < 0) {
+    x *= -1;
+    isNegetive = 1;
+  }
+  let reverse = 0;
+  while (x >= 1) {
+    const r = Math.floor(x % 10);
+    reverse = reverse * 10 + r;
+    x = Math.floor(x / 10);
+  }
+  if (reverse > 0x7fffffff) {
+    return 0;
+  }
+  return isNegetive ? reverse * -1 : reverse;
+}
+
 module.exports = {
   reverseNumber,
+  reverse32BitInt
 };

src/_Problems_/reverse-number/reverse-number.test.js

@@ -1,23 +1,43 @@
-const { reverseNumber } = require('.');
+const { reverseNumber, reverse32BitInt } = require('.');
 
 describe('Reverse Numbers', () => {
-  it('Should return a number', () => {
-    expect(typeof reverseNumber(1) === 'number');
-  });
+  describe('Normal Reverse', () => {
+    it('Should return a number', () => {
+      expect(typeof reverseNumber(1) === 'number');
+    });
 
-  it('Should reverse 45 to 54', () => {
-    expect(reverseNumber(45)).toEqual(54);
-  });
+    it('Should reverse 45 to 54', () => {
+      expect(reverseNumber(45)).toEqual(54);
+    });
 
-  it('Should reverse -2 to -2', () => {
-    expect(reverseNumber(-2)).toEqual(-2);
-  });
+    it('Should reverse -2 to -2', () => {
+      expect(reverseNumber(-2)).toEqual(-2);
+    });
+
+    it('Should reverse -1234567 to -7654321', () => {
+      expect(reverseNumber(-1234567)).toEqual(-7654321);
+    });
 
-  it('Should reverse -1234567 to -7654321', () => {
-    expect(reverseNumber(-1234567)).toEqual(-7654321);
+    it('Should throw error for invalid argument', () => {
+      expect(() => reverseNumber('hello')).toThrow('Invalid Argument');
+    });
   });
 
-  it('Should throw error for invalid argument', () => {
-    expect(() => reverseNumber('hello')).toThrow('Invalid Argument');
+  describe('32-bit signed integer reversal', () => {
+    it('Should return a number', () => {
+      expect(typeof reverse32BitInt(1) === 'number');
+    });
+
+    it('Should reverse 123 to 321', () => {
+      expect(reverse32BitInt(123)).toEqual(321);
+    });
+
+    it('Should reverse -871 to -178', () => {
+      expect(reverse32BitInt(-871)).toEqual(-178);
+    });
+
+    it('Should return 0 for 1534236469 because of overflow when reversed', () => {
+      expect(reverse32BitInt(1534236469)).toEqual(0);
+    });
   });
 });