diff --git a/docs/hackerrank/interview_preparation_kit/arrays/crush.md b/docs/hackerrank/interview_preparation_kit/arrays/crush.md new file mode 100644 index 00000000..fadf24af --- /dev/null +++ b/docs/hackerrank/interview_preparation_kit/arrays/crush.md @@ -0,0 +1,85 @@ +# [Arrays: Array Manipulation](https://www.hackerrank.com/challenges/crush) + +Perform m operations on an array and print the maximum of the values. + +- Difficulty: ` #hard ` +- Category: ` #ProblemSolvingIntermediate ` + +Starting with a 1-indexed array of zeros and a list of operations, for each +operation add a value to each the array element between two given indices, +inclusive. Once all operations have been performed, return the maximum +value in the array. + +## Example + +Queries are interpreted as follows: + +```text + a b k + 1 5 3 + 4 8 7 + 6 9 1 +``` + +Add the values of between the indices and inclusive: + +```text +index-> 1 2 3 4 5 6 7 8 9 10 + [0,0,0, 0, 0,0,0,0,0, 0] + [3,3,3, 3, 3,0,0,0,0, 0] + [3,3,3,10,10,7,7,7,0, 0] + [3,3,3,10,10,8,8,8,1, 0] +``` + +The largest value is `10` after all operations are performed. + +## Function Description + +Complete the function arrayManipulation in the editor below. + +arrayManipulation has the following parameters: + +- `int n` - the number of elements in the array +- `int queries[q][3]` - a two dimensional array of queries where +each `queries[i]` contains three integers, `a`, `b`, and `k`. + +## Returns + +- int - the maximum value in the resultant array + +## Input Format + +The first line contains two space-separated integers `n` and `m`, the size of +the array and the number of operations. +Each of the next `m` lines contains three space-separated integers +`a`, `b` and `k`, the left index, right index and summand. + +## Constraints + +- $ 3 \leq n \leq 10^7 $ +- $ 1 \leq m \leq 2*10^5 $ +- $ 1 \leq a \leq b \leq n $ +- $ 0 \leq k \leq 10^9 $ + +## Sample Input + +```text +5 3 +1 2 100 +2 5 100 +3 4 100 +``` + +## Sample Output + +```text +200 +```` + +## Explanation + +After the first update the list is `100 100 0 0 0`. +After the second update list is `100 200 100 100 100`. +After the third update list is `100 200 200 200 100`. + +The maximum value is `200`. diff --git a/docs/hackerrank/interview_preparation_kit/arrays/crush_optimized-solution-notes.md b/docs/hackerrank/interview_preparation_kit/arrays/crush_optimized-solution-notes.md new file mode 100644 index 00000000..c22f0d9b --- /dev/null +++ b/docs/hackerrank/interview_preparation_kit/arrays/crush_optimized-solution-notes.md @@ -0,0 +1,37 @@ +# [Array Manipulation](https://www.hackerrank.com/challenges/crush) + +Perform m operations on an array and print the maximum of the values. + +- Difficulty: ` #hard ` +- Category: ` #ProblemSolvingIntermediate ` + +## Solution sources + +### Brute force idea + +The first solution attempt is based on the idea of going through: + +> each row and then, +> > each sub-set of elements affected by the operation. + +With this principle, the algorithm becomes O(N^2) + +### Optimized + +Reading about posible optimizations, +I found the possibility of summarizing the interior traversal with +addition operations for each element in each row of operations, +in only 2 constant operations, which represents the necessary values so that +in a single final traversal, the sum values can be obtained "by drag". +The algorithm is called "prefix sum." + +Some sources about "prefix sum" + +- +- +- + +Some sources about implementation in: + +- [HackerRank Array Manipulation — beat the clock using Prefix Sum (JavaScript)](https://medium.com/@mlgerardvla/hackerrank-array-manipulation-beat-the-clock-using-prefix-sum-92471060035e) +- [Hackerrank Discussions Forums: Array Manipulation](https://www.hackerrank.com/challenges/one-month-preparation-kit-crush/forum) diff --git a/src/hackerrank/interview_preparation_kit/arrays/cruch_bruteforce.test.ts b/src/hackerrank/interview_preparation_kit/arrays/cruch_bruteforce.test.ts new file mode 100644 index 00000000..f4437b7d --- /dev/null +++ b/src/hackerrank/interview_preparation_kit/arrays/cruch_bruteforce.test.ts @@ -0,0 +1,22 @@ +import { describe, expect, it } from '@jest/globals'; +import { logger as console } from '../../../logger'; + +import { default as TEST_CASES } from './cruch_testcases_test.json'; + +import { arrayManipulation } from './cruch_bruteforce'; + +describe('arrays: crush (bruteforce) small cases', () => { + it('arrayManipulation Test Cases', () => { + expect.assertions(3); + + TEST_CASES.forEach((test) => { + const answer = arrayManipulation(test.n, test.queries); + + console.debug( + `rotLeftOne(${test.n}, ${test.queries}) solution found: ${answer}` + ); + + expect(answer).toStrictEqual(test.expected); + }); + }); +}); diff --git a/src/hackerrank/interview_preparation_kit/arrays/cruch_bruteforce.ts b/src/hackerrank/interview_preparation_kit/arrays/cruch_bruteforce.ts new file mode 100644 index 00000000..2b3f9444 --- /dev/null +++ b/src/hackerrank/interview_preparation_kit/arrays/cruch_bruteforce.ts @@ -0,0 +1,29 @@ +/** + * @link Problem definition [[docs/hackerrank/interview_preparation_kit/arrays/crush.md]] + * @see Solution Notes: [[docs/hackerrank/interview_preparation_kit/arrays/crush_optimized-solution-notes.md]] + */ + +import { logger as console } from '../../../logger'; + +export function arrayManipulation(n: number, queries: number[][]): number { + const LENGTH = n + 1; + const SURROGATE_VALUE = 0; + const result = Array(LENGTH).fill(SURROGATE_VALUE); + let maximum = 0; + + queries.forEach((query) => { + const [a_start, b_end, k_value] = query; + console.debug(`start -> ${result}`); + + for (let i = a_start; i <= b_end; i++) { + result[i] += k_value; + console.debug(`result -> ${result}`); + } + }); + + result.forEach((value) => { + maximum = Math.max(value, maximum); + }); + + return maximum; +} diff --git a/src/hackerrank/interview_preparation_kit/arrays/cruch_optimized.test.ts b/src/hackerrank/interview_preparation_kit/arrays/cruch_optimized.test.ts new file mode 100644 index 00000000..1a2779dc --- /dev/null +++ b/src/hackerrank/interview_preparation_kit/arrays/cruch_optimized.test.ts @@ -0,0 +1,22 @@ +import { describe, expect, it } from '@jest/globals'; +import { logger as console } from '../../../logger'; + +import { default as TEST_CASES } from './cruch_testcases_test.json'; + +import { arrayManipulation } from './cruch_optimized'; + +describe('arrays: crush (optimized)', () => { + it('arrayManipulation Test Cases', () => { + expect.assertions(3); + + TEST_CASES.forEach((test) => { + const answer = arrayManipulation(test.n, test.queries); + + console.debug( + `rotLeftOne(${test.n}, ${test.queries}) solution found: ${answer}` + ); + + expect(answer).toStrictEqual(test.expected); + }); + }); +}); diff --git a/src/hackerrank/interview_preparation_kit/arrays/cruch_optimized.ts b/src/hackerrank/interview_preparation_kit/arrays/cruch_optimized.ts new file mode 100644 index 00000000..77fc622a --- /dev/null +++ b/src/hackerrank/interview_preparation_kit/arrays/cruch_optimized.ts @@ -0,0 +1,29 @@ +/** + * @link Problem definition [[docs/hackerrank/interview_preparation_kit/arrays/crush.md]] + */ + +export function arrayManipulation(n: number, queries: number[][]): number { + // why adding 2? + // first slot to adjust 1-based index and + // last slot for storing accum_sum result + const LENGTH = n + 2; + const INITIAL_VALUE = 0; + const result = Array(LENGTH).fill(INITIAL_VALUE); + let maximum = 0; + + queries.forEach((query) => { + const [a_start, b_end, k_value] = query; + + result[a_start] += k_value; + result[b_end + 1] -= k_value; + }); + + let accum_sum = 0; + + result.forEach((value) => { + accum_sum += value; + maximum = Math.max(maximum, accum_sum); + }); + + return maximum; +} diff --git a/src/hackerrank/interview_preparation_kit/arrays/cruch_testcases_test.json b/src/hackerrank/interview_preparation_kit/arrays/cruch_testcases_test.json new file mode 100644 index 00000000..ec7d19ca --- /dev/null +++ b/src/hackerrank/interview_preparation_kit/arrays/cruch_testcases_test.json @@ -0,0 +1,73 @@ +[ + { + "title": "Sample Test Case 0", + "n": 5, + "queries": [ + [ + 1, + 2, + 100 + ], + [ + 2, + 5, + 100 + ], + [ + 3, + 4, + 100 + ] + ], + "expected": 200 + }, + { + "title": "Sample Test Case 1", + "n": 10, + "queries": [ + [ + 1, + 5, + 3 + ], + [ + 4, + 8, + 7 + ], + [ + 6, + 9, + 1 + ] + ], + "expected": 10 + }, + { + "title": "Sample Test Case 3", + "n": 10, + "queries": [ + [ + 2, + 6, + 8 + ], + [ + 3, + 5, + 7 + ], + [ + 1, + 8, + 1 + ], + [ + 5, + 9, + 15 + ] + ], + "expected": 31 + } +]