[Hacker Rank] Interview Preparation Kit: Sorting: Bubble Sort. Solved ✅.

Author: Gonzalo Diaz

docs/hackerrank/interview_preparation_kit/sort/ctci-bubble-sort.md

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+# [Sorting: Bubble Sort](https://www.hackerrank.com/challenges/ctci-bubble-sort/)
+
+Find the minimum number of conditional checks taking place in Bubble Sort
+
+- Difficulty:  `#easy`
+- Category: `#ProblemSolvingBasic` `#sorting`
+
+Consider the following version of Bubble Sort:
+
+```c
+for (int i = 0; i < n; i++) {
+
+    for (int j = 0; j < n - 1; j++) {
+        // Swap adjacent elements if they are in decreasing order
+        if (a[j] > a[j + 1]) {
+            swap(a[j], a[j + 1]);
+        }
+    }
+
+}
+```
+
+Given an array of integers, sort the array in ascending order
+using the Bubble Sort algorithm above. Once sorted, print the following three lines:
+
+1. `Array is sorted in numSwaps swaps.`, where *`numSums`* is
+the number of swaps that took place.
+2. `First Element: firstElement`, where *`firstElement`* is
+the first element in the sorted array.
+3. `Last Element: lastElement`, where *`lastElement`* is
+the last element in the sorted array.
+
+**Hint**: To complete this challenge, you must add a variable
+that keeps a running tally of all swaps that occur during execution.
+
+## Example
+
+```text
+swap    a
+0       [6,4,1]
+1       [4,6,1]
+2       [4,1,6]
+3       [1,4,6]
+```
+
+The steps of the bubble sort are shown above. It took `3` swaps to sort the array.
+Output is:
+
+```text
+Array is sorted in 3 swaps.
+First Element: 1
+Last Element: 6
+```
+
+## Function Description
+
+Complete the function countSwaps in the editor below.
+
+countSwaps has the following parameter(s):
+
+- `int a[n]`: an array of integers to sort
+
+## Prints
+
+Print the three lines required, then return. No return value is expected.
+
+## Input Format
+
+The first line contains an integer, `n`, the size of the array `a`.
+The second line contains `n` space-separated integers `a[i]`.
+
+## Constraints
+
+- $ 2 \leq n \leq 600 $
+- $ a \leq a[i] \leq 2 \times 10^6 $
+
+## Output Format
+
+## Sample Input 0
+
+```text
+STDIN   Function
+-----   --------
+3       a[] size n = 3
+1 2 3   a = [1, 2, 3]
+```
+
+## Sample Output 0
+
+```text
+Array is sorted in 0 swaps.
+First Element: 1
+Last Element: 3
+Explanation 0
+```
+
+The array is already sorted, so `0` swaps take place.
+
+## Sample Input 1
+
+```text
+3
+3 2 1
+```
+
+## Sample Output 1
+
+```text
+Array is sorted in 3 swaps.
+First Element: 1
+Last Element: 3
+```
+
+## Explanation 1
+
+The array is not sorted, and its initial values are: `{1, 2, 3}`.
+The following `3` swaps take place:
+
+```text
+{3, 2, 1} -> {2, 3, 1}
+{2, 3, 1} -> {2, 1, 3}
+{2, 1, 3} -> {1, 2, 3}
+```
+
+At this point the array is sorted and the three lines of output are printed to stdout.

src/hackerrank/interview_preparation_kit/sort/ctci_bubble_sort.test.ts

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+import { describe, expect, it } from '@jest/globals';
+
+import { countSwaps, SortableGroup } from './ctci_bubble_sort';
+import TEST_CASES from './ctci_bubble_sort.testcases.json';
+
+describe('countSwaps', () => {
+  it('build tree and flattened tree test cases', () => {
+    expect.assertions(6);
+
+    TEST_CASES.forEach((test) => {
+      const sortable = new SortableGroup(test.input);
+      const resultSort = sortable.bubble_sort().group;
+      const resultPrint = countSwaps(test.input);
+
+      expect(resultPrint).toBeUndefined();
+      expect(resultSort).toStrictEqual(test.sorted);
+    });
+  });
+});

src/hackerrank/interview_preparation_kit/sort/ctci_bubble_sort.testcases.json

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+[
+  {
+    "input": [6, 4, 1],
+    "sorted": [1, 4, 6],
+    "expected": "Array is sorted in 3 swaps.\nFirst Element: 1\nLast Element: 6\n"
+  },
+  {
+    "input": [3, 2, 1],
+    "sorted": [1, 2, 3],
+    "expected": "Array is sorted in 3 swaps.\nFirst Element: 1\nLast Element: 3\n"
+  },
+  {
+    "input": [1, 2, 3],
+    "sorted": [1, 2, 3],
+    "expected": "Array is sorted in 0 swaps.\nFirst Element: 1\nLast Element: 3\n"
+  }
+]

src/hackerrank/interview_preparation_kit/sort/ctci_bubble_sort.ts

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+/**
+ * @link Problem definition [[docs/hackerrank/interview_preparation_kit/sort/ctci-bubble-sort.md]]
+ */
+
+const SEPARATOR = '\n';
+
+export class SortableGroup {
+  group: number[];
+
+  count: number;
+
+  constructor(group: number[]) {
+    this.count = 0;
+    this.group = group;
+  }
+
+  bubble_sort(): this {
+    const group = [...this.group];
+    const size: number = group.length;
+    let count = 0;
+    let i = 0;
+
+    while (i < size) {
+      for (let j = 0; j < size - 1; j++) {
+        if (group[j] > group[j + 1]) {
+          [group[j], group[j + 1]] = [group[j + 1], group[j]];
+
+          count += 1;
+        }
+      }
+      i += 1;
+    }
+
+    this.count = count;
+    this.group = group;
+
+    return this;
+  }
+}
+
+export function countSwaps(a: number[]): void {
+  const sortableGroup = new SortableGroup(a);
+  sortableGroup.bubble_sort();
+
+  const last = sortableGroup.group.length - 1;
+
+  const output =
+    `Array is sorted in ${sortableGroup.count} swaps.${SEPARATOR}` +
+    `First Element: ${sortableGroup.group[0]}${SEPARATOR}` +
+    `Last Element: ${sortableGroup.group[last]}${SEPARATOR}`;
+
+  console.log(output);
+}
+
+export default { countSwaps, SortableGroup };