Integer to Roman (js) – ALPHA Camp

    AllenLi
    CodingLeetCode Js-String

    了解題意

    Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

    
Symbol       Value
I             1
V             5
X             10
L             50
C             100
D             500
M             1000

    將用到以下方法完成計算：

    1. Math.floor() => 函式會回傳小於等於所給數字的最大整數。
2. !== => 嚴格的不等於。
3. === => 嚴格的等於。
4. %= => 等同 x = x % y，取餘數。(ex. 2439 / 1000 = 439)
5. for (key in x) & key.repeat 
=> 依序將 x 中的key值帶入迴圈，同時確認key值重複放入次數，並更新至romanNumber=''中。

    Let’s imagine we need to convert
    ( No.1 : 2999 ; No.2 : 0 )

    Code 1:

    function toRoman(num){
  const romanMap = { //宣告羅馬數字的特殊字串對應阿拉伯數字
    M: 1000,
    CM: 900,
    D: 500,
    CD: 400,
    C: 100,
    XC: 90,
    L: 50,
    XL: 40,
    X: 10,
    IX: 9,
    V: 5,
    IV: 4,
    I: 1
  }

  let romanNumber = '' //宣告字串空間
  
  for (let key in romanMap) {
    let repeatCounter = Math.floor(num / romanMap[key]) //確認num被romanMap[key]整除的次數

    if (repeatCounter !== 0) { //如果次數不是「0」
      romanNumber += key.repeat(repeatCounter) //則執行取字串*次數
    }
    num %= romanMap[key] // x = x % y 更新num等於餘數
    if (num === 0) return romanNumber //如果次數等於「0」，回傳romanNumber=''的值
  }
return romanNumber
}

    No.1 驗證「2999」迴圈過程：

    迴圈.1
Math.floor(2999 / 1000) = 2
result += M.repeat(2) = MM
2999 = 2999 % 1000 = 999

迴圈.2
Math.floor(999 / 900) = 1
result += CM.repeat(1) = MMCM
999 = 999 % 900 = 99

迴圈.3
Math.floor(99 / 500) = 0
result += D.repeat(0) = MMCM
99 = 99 % 500 = 99

迴圈.4
Math.floor(99 / 400) = 0
result += CD.repeat(0) = MMCM
99 = 99 % 400 = 99

迴圈.5
Math.floor(99 / 100) = 0
result += C.repeat(0) = MMCM
99 = 99 % 100 = 99

迴圈.6
Math.floor(99 / 90) = 1
result += XC.repeat(1) = MMCMXC
99 = 99 % 90 = 9

迴圈.7
Math.floor(9 / 50) = 0
result += L.repeat(0) = MMCMXC
9 = 9 % 50 = 9

迴圈.8
Math.floor(9 / 40) = 0
result += XL.repeat(0) = MMCMXC
9 = 9 % 40 = 9

迴圈.9
Math.floor(9 / 10) = 0
result += X.repeat(0) = MMCMXC
9 = 9 % 10 = 9

迴圈.10
Math.floor(9 / 9) = 1
result += IX.repeat(1) = MMCMXCIX
9 = 9 % 9 = 0

迴圈.11
Math.floor(0 / 5) = 0
result += V.repeat(0) = MMCMXCIX
0 = 0 % 5 = 0

迴圈.12
Math.floor(0 / 4) = 0
result += IV.repeat(0) = MMCMXCIX
0 = 0 % 4 = 0

迴圈.13
Math.floor(0 / 1) = 0
result += I.repeat(0) = MMCMXCIX
0 = 0 % 1 = 0

    No.2 驗證「0」迴圈過程：

    
Math.floor(0 / 1) = 0
result += I.repeat(0) = ''
0 = 0 % 1 = 0

    ex. Integer to Roman (點我.replit)

    Code 2:

    function intToRoman(num: number): string {
  const romanMap: [string, number][] = [
    ["M", 1000],
    ["CM", 900], 
    ["D", 500],
    ["CD", 400], 
    ["C", 100],
    ["XC", 90],  
    ["L", 50],
    ["XL", 40],  
    ["X", 10],
    ["IX", 9],   
    ["V", 5],
    ["IV", 4],   
    ["I", 1],
  ];

  let romanNumber = "";

  for (const [symbol, value] of romanMap) {
    const repeatCounter = Math.floor(num / value);
    num %= value;
    romanNumber += symbol.repeat(repeatCounter);
    if (num === 0) break; 
  }

  return romanNumber;
}

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