HackerRank Js-Week2 8. Mars Exploration

    AllenLi
    HackerRank

    A space explorer’s ship crashed on Mars! They send a series of SOS messages to Earth for help.
    Letters in some of the SOS messages are altered by cosmic radiation during transmission. Given the signal received by Earth as a string, s, determine how many letters of the SOS message have been changed by radiation.

    一個太空探索者的飛船墜毀在火星上！他們向地球發送一系列 SOS 信息尋求協助。
在 SOS 信息字母在傳輸過程中會被宇宙輻射改變。給予地球以字母形式接收的信號 s，確定 SOS 信息中有多少字母因輻設而改變。

    Example 1:

    s = "SOSTOT"
The original message was SOSSOS. Two of the message's characters were changed in transit.

    solution:
    試著將 SOS 標準信息找出規律，以此將遍歷的過程以三元運算式判斷，
    發現只要是 3 的倍數且餘 1，如符合則為 “O”，不符合則為 “S”。
    後續確認遍歷過程中，不符合標準信息之字母，運用 count += 1 紀錄後回傳。

    S O S S O S S O S S  O  S  S  O
0 1 2 3 4 5 6 7 8 9 10 11 12 13

    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 'marsExploration' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts STRING s as parameter.
 */

function marsExploration(s) {
    // Write your code here
    let count = 0
    
    for (let i = 0; i < s.length; i++) {
      let letter = (i % 3 === 1) ? "O" : "S"
      
      if (s.charAt(i) !== letter) count++
    }
    return count;
}

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

    const s = readLine();

    const result = marsExploration(s);

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

    ws.end();
}

    FlowChart:
    Example 1

    s = "SOSTOT"

STD = "SOSSOS"
s   = "SOSTOT
return count //2

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