HackerRank Js-Week4 2. Left Rotation

    AllenLi
    HackerRank

    A left rotation operation on an array of size n shifts each of the array’s elements 1 unit to the left. Given an integer, d, rotate the array that many steps left and return the result.

    一個大小為 n 的陣列進行左旋轉操作，將陣列中的每個元素向左移動 1 個單位。
給予一個整數 d，旋轉陣列剩餘的步數並回傳結果。

    Example 1:

    d = 2
arr = [1, 2, 3, 4, 5]

After 2 rotations, arr' = [3, 4, 5, 1, 2].

    solution:
    運用 javascript 的原生語法函式將陣列元素進行指定位置的切割，
    最後用 concat 來重新組合兩個陣列。

    Code 1: BigO(n)

    'use strict';

const fs = require('fs');

process.stdin.resume();
process.stdin.setEncoding('utf-8');

let inputString = '';
let currentLine = 0;

process.stdin.on('data', function(inputStdin) {
    inputString += inputStdin;
});

process.stdin.on('end', function() {
    inputString = inputString.split('\n');

    main();
});

function readLine() {
    return inputString[currentLine++];
}

/*
 * Complete the 'rotateLeft' function below.
 *
 * The function is expected to return an INTEGER_ARRAY.
 * The function accepts following parameters:
 *  1. INTEGER d
 *  2. INTEGER_ARRAY arr
 */

function rotateLeft(d, arr) {
    // Write your code here
    const array = [...arr]
    const fisrtPart = array.slice(0, d)
    const secondPart = array.slice(d)
    return secondPart.concat(fisrtPart)
}

function main() {
    const ws = fs.createWriteStream(process.env.OUTPUT_PATH);

    const firstMultipleInput = readLine().replace(/\s+$/g, '').split(' ');

    const n = parseInt(firstMultipleInput[0], 10);

    const d = parseInt(firstMultipleInput[1], 10);

    const arr = readLine().replace(/\s+$/g, '').split(' ').map(arrTemp => parseInt(arrTemp, 10));

    const result = rotateLeft(d, arr);

    ws.write(result.join(' ') + '\n');

    ws.end();
}

    FlowChart:
    Example 1

    d = 2
array = [1, 2, 3, 4, 5]

fisrtPart = array.slice(0, d) //array.slice(0, 2) [1, 2]
secondPart = array.slice(d) //array.slice(2) [3, 4, 5]

return secondPart.concat(fisrtPart) //[3, 4, 5, 1, 2]

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