HackerRank Js-Week4 7. Minimum Absolute Difference in an Array

    AllenLi
    HackerRank

    The absolute difference is the positive difference between two values a and b, is written |a – b| or |b – a| and they are equal. If a = 3 and b = 2, |3 – 2| = |2 – 3|. Given an array of integers, find the minimum absolute difference between any two elements in the array.

    絕對差是兩個值 a 和 b 之間的差，
被寫成 |a - b| 或 |b - a| 並且它們是相等的。 
如果 a = 3 且 b = 2，|3 - 2| = |2 - 3|。 
給與一個整數陣列，找到數組中任意兩個元素之間的最小絕對差。

    Example 1:

    arr = [-2, 2, 4]

There are 3 pairs of numbers: |-2, 2|, |-2, 4| and [2, 4]. The absolute differences for these pairs are |(-2) - 2| = 4, |(-2) - 4| = 6 and |2 - 4| = 2. The minimum absolute difference is 2.

    solution:
    先用 sort() 將陣列排序由小到大，接著宣告變數 min 為無窮大(Infinity)，
    這樣第一次比對時可以找到最小值，後續使用for迴圈遍歷陣列中的元素。
    每次迭代中，獲取當前元素 curr 和下一個元素 next，並計算他們之間的絕對差 diff。
    回傳 min 最小的絕對差。

    Code 1: BigO(n log 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 'minimumAbsoluteDifference' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts INTEGER_ARRAY arr as parameter.
 */

function minimumAbsoluteDifference(arr) {
    // Write your code here
    arr.sort((a, b) => a - b)
    let min = Infinity;
    for(let i = 0; i < arr.length;i++) {
        const curr = arr[i]
        const next = arr[i + 1]
        const diff = Math.abs(curr - next)
        if(diff < min) {
            min = diff
        }
    }
    return min;
}

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

    const n = parseInt(readLine().trim(), 10);

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

    const result = minimumAbsoluteDifference(arr);

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

    ws.end();
}

    FlowChart:
    Example 1

    arr = [-2, 2, 4]

curr = -2
next = 2
diff = Math.abs(curr - next) //|-2 - 2| = 4
diff < min //4 < Infinity
min = 4

curr = 2
next = 4
diff = Math.abs(curr - next) //|2 - 4| = 2
diff < min //2 < 4
min = 2

return min; //2

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