[Hacker Rank] Interview Preparation Kit: Miscellaneous: Flipping bits. Solved ✅.

Author: Gonzalo Diaz

docs/hackerrank/miscellaneous/flipping-bits.md

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+# [Miscellaneous: Flipping bits](https://www.hackerrank.com/challenges/flipping-bits)
+
+- Difficulty:  `#easy`
+- Category: `#ProblemSolvingBasic` `#BitManipulation`
+
+You will be given a list of 32 bit unsigned integers.
+Flip all the bits ( `1 -> 0` and `0 -> 1`)
+and return the result as an unsigned integer.
+
+## Example
+
+$ n = 9_{10} $. We're working with 32 bits, so:
+
+$ 9_{10} = 1001_{2} $
+
+$ 00000000000000000000000000001001_{2} = 9_{10} $
+$ 11111111111111111111111111110110_{2} = 4294967286_{10} $
+
+Return `4294967286`
+
+## Function Description
+
+Complete the flippingBits function in the editor below.
+
+flippingBits has the following parameter(s):
+
+- `int n`: an integer
+
+## Returns
+
+- `int`: the unsigned decimal integer result
+
+## Input Format
+
+The first line of the input contains `q`, the number of queries.
+Each of the next `q` lines contain an integer, `n`, to process.
+
+## Constraints
+
+- $ 1 \leq q \leq 100 $
+- $ 0 \leq n \leq 2^{32} $
+
+## Sample Input 0
+
+```text
+3
+2147483647
+1
+0
+```
+
+## Sample Output 0
+
+```text
+2147483648
+4294967294
+4294967295
+```
+
+## Explanation 0
+
+$ 01111111111111111111111111111111_{2} = 2147483647_{10} $
+$ 10000000000000000000000000000000_{2} = 2147483648_{10} $
+
+$ 00000000000000000000000000000001_{2} = 1_{10} $
+$ 11111111111111111111111111111110_{2} = 4294967294_{10} $
+
+$ 00000000000000000000000000000000_{2} = 0_{10} $
+$ 11111111111111111111111111111110_{2} = 4294967295_{10} $
+
+## Sample Input 1
+
+```text
+2
+4
+123456
+```
+
+## Sample Output 1
+
+```text
+4294967291
+4294843839
+```
+
+## Explanation 1
+
+$ 00000000000000000000000000000100_{2} = 4_{10} $
+$ 11111111111111111111111111111011_{2} = 4294967291_{10} $
+
+$ 00000000000000011110001001000000_{2} = 4_{10} $
+$ 11111111111111100001110110111111_{2} = 429484389_{10} $
+
+## Sample Input 2
+
+```text
+3
+0
+802743475
+35601423
+```
+
+## Sample Output 2
+
+```text
+4294967295
+3492223820
+4259365872
+```
+
+## Explanation 2
+
+$ 00000000000000000000000000000000_{2} = 4_{10} $
+$ 11111111111111111111111111111111_{2} = 4294967295_{10} $
+
+$ 00101111110110001110010010110011_{2} = 802743475_{10} $
+$ 11010000001001110001101101001100_{2} = 3492223820_{10} $
+
+$ 00000010000111110011110000001111_{2} = 35601423_{10} $
+$ 11111101111000001100001111110000_{2} = 4259365872_{10} $

src/hackerrank/interview_preparation_kit/miscellaneous/flipping-bits.test.ts

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+import { describe, expect, it } from '@jest/globals';
+import { logger as console } from '../../../logger';
+
+import { flippingBits } from './flipping-bits';
+
+const TEST_CASES = [
+  {
+    title: 'Sample Test Case 0',
+    tests: [
+      {
+        input: 2147483647,
+        expected: 2147483648
+      },
+      {
+        input: 1,
+        expected: 4294967294
+      },
+      {
+        input: 0,
+        expected: 4294967295
+      }
+    ]
+  },
+  {
+    title: 'Sample Test Case 1',
+    tests: [
+      {
+        input: 4,
+        expected: 4294967291
+      },
+      {
+        input: 123456,
+        expected: 4294843839
+      }
+    ]
+  },
+  {
+    title: 'Sample Test Case 2',
+    tests: [
+      {
+        input: 0,
+        expected: 4294967295
+      },
+      {
+        input: 802743475,
+        expected: 3492223820
+      },
+      {
+        input: 35601423,
+        expected: 4259365872
+      }
+    ]
+  }
+];
+
+describe('flipping bits', () => {
+  it('flipping bits test cases', () => {
+    expect.assertions(8);
+
+    TEST_CASES.forEach((test_set) => {
+      test_set.tests.forEach((test) => {
+        const answer = flippingBits(test.input);
+
+        console.debug(`luckBalance(${test.input}) solution found: ${answer}`);
+
+        expect(answer).toStrictEqual(test.expected);
+      });
+    });
+  });
+
+  it('flipping bits isolated test case', () => {
+    expect.assertions(1);
+
+    const input = 9;
+    const expected = 4294967286;
+
+    const answer = flippingBits(input);
+
+    console.debug(`luckBalance(${input}) solution found: ${answer}`);
+
+    expect(answer).toStrictEqual(expected);
+  });
+});

src/hackerrank/interview_preparation_kit/miscellaneous/flipping-bits.ts

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+/**
+ * @link Problem definition [[docs/hackerrank/miscellaneous/flipping-bits.md]]
+ */
+
+const __BINARY_BASE__ = 2;
+const __NUMBER_SIZE_IN_BITS__ = 32;
+
+export function flippingBits(n: number): number {
+  let n_binary_str = n.toString(__BINARY_BASE__);
+  n_binary_str = n_binary_str.padStart(__NUMBER_SIZE_IN_BITS__, '0');
+
+  let result_bin_str = '';
+
+  n_binary_str.split('').forEach((bin_digit) => {
+    if (bin_digit == '1') {
+      result_bin_str += '0';
+    } else {
+      result_bin_str += '1';
+    }
+  });
+
+  return parseInt(result_bin_str, __BINARY_BASE__);
+}
+
+export default { flippingBits };