add: rotate image solution and testing suite #192 #193

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		- [Maximum Product of Three Numbers](src/_Problems_/max-product-of-3-numbers)
		- [Next Greater for Every Element in an Array](src/_Problems_/next-greater-element)
		- [Compose Largest Number](src/_Problems_/compose-largest-number)
	- [Rotate Image](src/_Problems_/rotate-image)

		### Searching

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83 changes: 83 additions & 0 deletions src/_Problems_/rotate-image/index.js

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	/*
	Rotate Image (LeetCode #48)

	- You are given an n x n 2D matrix representing an image, rotate the
	image by 90 degrees (clockwise).
	- You have to rotate the image in-place, which means you have to modify
	the input 2D matrix directly. DO NOT allocate another 2D matrix and do
	the rotation.

	Example 1:

	1 2 3 7 4 1
	4 5 6 ---> 8 5 2
	7 8 9 9 6 3

	- Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
	- Output: [[7,4,1],[8,5,2],[9,6,3]]

	Example 2:

	5 1 9 11 15 13 2 5
	2 4 8 10 ---> 14 3 4 1
	13 3 6 7 12 6 8 9
	15 14 12 16 16 7 10 11

	- Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
	- Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]

	Constraints:
	- n == matrix.length == matrix[i].length
	- 1 <= n <= 20
	- -1000 <= matrix[i][j] <= 1000
	*/

	/*
	Solution:

	1. First, take the transpose of the matrix
	- Example:
	1 2 3 1 4 7
	4 5 6 ---> 2 5 8
	7 8 9 3 6 9

	2. Second, flip the matrix horizontally
	- Example:
	1 4 7 7 4 1
	2 5 8 ---> 8 5 2
	3 6 9 9 6 3

	3. Problem solved!

	- Solution is O(n) where n is the size (total number of entries) of the
	input matrix
	*/

	function rotateImage(matrix) {
	const n = matrix.length;

	// take transpose
	for (let i = 0; i < n; i++) {
	for (let j = i; j < n; j++) {
	const temp = matrix[i][j];
	matrix[i][j] = matrix[j][i];
	matrix[j][i] = temp;
	}
	}

	// flip horizontally
	for (let i = 0; i < n; i++) {
	let left = 0;
	let right = n - 1;

	while (left < right) {
	const temp = matrix[i][left];
	matrix[i][left] = matrix[i][right];
	matrix[i][right] = temp;
	left++;
	right--;
	}
	}
	}

	module.exports = { rotateImage };

58 changes: 58 additions & 0 deletions src/_Problems_/rotate-image/rotate-image.test.js

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	const { rotateImage } = require('.');

	describe('Rotate Image', () => {
	it('Should rotate 3x3 matrix elements by 90 degrees', () => {
	const inputMatrix = [
	[1, 2, 3],
	[4, 5, 6],
	[7, 8, 9],
	];

	const expectedMatrix = [
	[7, 4, 1],
	[8, 5, 2],
	[9, 6, 3],
	];

	rotateImage(inputMatrix);
	expect(inputMatrix).toEqual(expectedMatrix);
	});
	it('Should rotate 4x4 matrix elements by 90 degrees', () => {
	const inputMatrix = [
	[5, 1, 9, 11],
	[2, 4, 8, 10],
	[13, 3, 6, 7],
	[15, 14, 12, 16],
	];

	const expectedMatrix = [
	[15, 13, 2, 5],
	[14, 3, 4, 1],
	[12, 6, 8, 9],
	[16, 7, 10, 11],
	];

	rotateImage(inputMatrix);
	expect(inputMatrix).toEqual(expectedMatrix);
	});
	it('Should rotate 5x5 matrix elements by 90 degrees', () => {
	const inputMatrix = [
	[1, 2, 3, 4, 5],
	[6, 7, 8, 9, 10],
	[11, 12, 13, 14, 15],
	[16, 17, 18, 19, 20],
	[21, 22, 23, 24, 25],
	];

	const expectedMatrix = [
	[21, 16, 11, 6, 1],
	[22, 17, 12, 7, 2],
	[23, 18, 13, 8, 3],
	[24, 19, 14, 9, 4],
	[25, 20, 15, 10, 5],
	];

	rotateImage(inputMatrix);
	expect(inputMatrix).toEqual(expectedMatrix);
	});
	});

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