12. Integer to Roman

Leetcode

https://leetcode.com/problems/integer-to-roman/

題目

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

For example, 2 is written as II in Roman numeral, just two one's added together. 12 is written as XII, which is simply X + II. The number 27 is written as XXVII, which is XX + V + II.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:

• I can be placed before V (5) and X (10) to make 4 and 9.

• X can be placed before L (50) and C (100) to make 40 and 90.

• C can be placed before D (500) and M (1000) to make 400 and 900.

Given an integer, convert it to a roman numeral.

解答

• 方法一

由於題目限制 1 <= num <= 3999，所以我們可以利用貪婪算法，arr 列出所有可能的狀況，再一一遍歷 arr 求出羅馬字母

var intToRoman = function(num) {
    const arr = [
        {
            symbol: 'M',
            value: 1000
        },
        {
            symbol: 'CM',
            value: 900
        },
        {
            symbol: 'D',
            value: 500
        },
        {
            symbol: 'CD',
            value: 400
        },
        {
            symbol: 'C',
            value: 100
        },
        {
            symbol: 'XC',
            value: 90
        },
        {
            symbol: 'L',
            value: 50
        },
        {
            symbol: 'XL',
            value: 40
        },
        {
            symbol: 'X',
            value: 10
        },
        {
            symbol: 'IX',
            value: 9
        },
        {
            symbol: 'V',
            value: 5
        },
        {
            symbol: 'IV',
            value: 4
        },
        {
            symbol: 'I',
            value: 1
        },
    ]
    
    let res = '';
    for(let i=0; i<arr.length; i++) {
        const obj = arr[i];
        let quotient = Math.floor(num / obj.value);
        while(quotient--) {
            res += obj.symbol;
            num -= obj.value;
        }
    }
    return res;
};

Runtime: 144 ms, faster than 71.19% of JavaScript online submissions for Integer to Roman.

Memory Usage: 45 MB, less than 71.48% of JavaScript online submissions for Integer to Roman.

測資

let num = 58; // "LVIII"
num = 1994; // "MCMXCIV"

console.log(intToRoman(num))

參考資料

https://www.cnblogs.com/grandyang/p/4123374.html