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Commit 6643c73

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add: rotate image problem, solution, and testing suite (#193)
Merging, thanks.
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‎TOC.md

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

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/*
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Rotate Image (LeetCode #48)
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- You are given an n x n 2D matrix representing an image, rotate the
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image by 90 degrees (clockwise).
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- You have to rotate the image in-place, which means you have to modify
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the input 2D matrix directly. DO NOT allocate another 2D matrix and do
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the rotation.
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Example 1:
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1 2 3 7 4 1
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4 5 6 ---> 8 5 2
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7 8 9 9 6 3
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- Input: matrix = [[1,2,3],[4,5,6],[7,8,9]]
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- Output: [[7,4,1],[8,5,2],[9,6,3]]
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Example 2:
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5 1 9 11 15 13 2 5
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2 4 8 10 ---> 14 3 4 1
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13 3 6 7 12 6 8 9
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15 14 12 16 16 7 10 11
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- Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
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- Output: [[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
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Constraints:
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- n == matrix.length == matrix[i].length
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- 1 <= n <= 20
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- -1000 <= matrix[i][j] <= 1000
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*/
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/*
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Solution:
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1. First, take the transpose of the matrix
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- Example:
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1 2 3 1 4 7
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4 5 6 ---> 2 5 8
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7 8 9 3 6 9
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2. Second, flip the matrix horizontally
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- Example:
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1 4 7 7 4 1
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2 5 8 ---> 8 5 2
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3 6 9 9 6 3
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3. Problem solved!
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- Solution is O(n) where n is the size (total number of entries) of the
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input matrix
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*/
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function rotateImage(matrix) {
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const n = matrix.length;
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// take transpose
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for (let i = 0; i < n; i++) {
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for (let j = i; j < n; j++) {
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const temp = matrix[i][j];
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matrix[i][j] = matrix[j][i];
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matrix[j][i] = temp;
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}
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}
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// flip horizontally
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for (let i = 0; i < n; i++) {
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let left = 0;
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let right = n - 1;
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while (left < right) {
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const temp = matrix[i][left];
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matrix[i][left] = matrix[i][right];
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matrix[i][right] = temp;
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left++;
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right--;
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}
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}
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}
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module.exports = { rotateImage };
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const { rotateImage } = require('.');
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describe('Rotate Image', () => {
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it('Should rotate 3x3 matrix elements by 90 degrees', () => {
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const inputMatrix = [
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[1, 2, 3],
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[4, 5, 6],
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[7, 8, 9],
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];
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const expectedMatrix = [
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[7, 4, 1],
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[8, 5, 2],
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[9, 6, 3],
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];
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rotateImage(inputMatrix);
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expect(inputMatrix).toEqual(expectedMatrix);
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});
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it('Should rotate 4x4 matrix elements by 90 degrees', () => {
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const inputMatrix = [
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[5, 1, 9, 11],
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[2, 4, 8, 10],
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[13, 3, 6, 7],
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[15, 14, 12, 16],
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];
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const expectedMatrix = [
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[15, 13, 2, 5],
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[14, 3, 4, 1],
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[12, 6, 8, 9],
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[16, 7, 10, 11],
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];
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rotateImage(inputMatrix);
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expect(inputMatrix).toEqual(expectedMatrix);
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});
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it('Should rotate 5x5 matrix elements by 90 degrees', () => {
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const inputMatrix = [
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[1, 2, 3, 4, 5],
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[6, 7, 8, 9, 10],
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[11, 12, 13, 14, 15],
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[16, 17, 18, 19, 20],
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[21, 22, 23, 24, 25],
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];
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const expectedMatrix = [
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[21, 16, 11, 6, 1],
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[22, 17, 12, 7, 2],
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[23, 18, 13, 8, 3],
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[24, 19, 14, 9, 4],
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[25, 20, 15, 10, 5],
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];
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rotateImage(inputMatrix);
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expect(inputMatrix).toEqual(expectedMatrix);
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});
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});

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