ローマへの整数

これは一連のleetcode解決説明の一部です.あなたがこの解決が好きであるか、それが役に立つとわかるならば、このポストとmy solution post on Leetcode's forums .

Leetcode Problem #12 (Medium): Integer to Roman

説明
にジャンプします.Solution Idea || コードJavaScript | Python | Java | C++ )

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.

例:

Example 1:
Input:	num = 3
Output:	"III"

Example 2:
Input:	num = 4
Output:	"IV"

Example 3:
Input:	num = 9
Output:	"IX"

Example 4:
Input:	num = 58
Output:	"LVIII"
Explanation:	L = 50, V = 5, III = 3.

Example 5:
Input:	num = 1994
Output:	"MCMXCIV"
Explanation:	M = 1000, CM = 900, XC = 90 and IV = 4.

制約

• 1 <= num <= 3999

考え
にジャンプします.Problem Description || コードJavaScript | Python | Java | C++ )
Randomと整数のように、この問題は最も簡単に数字と数字の間の変換のためのルックアップテーブルを使用して解決されます.この場合、我々は容易に降順で値を扱うことができます、そして、同じ量によって我々の目標数(n)を減らしている間、適切な数字(または数)を我々ができるだけ多くの倍に挿入することができます.
nがなくなると、私たちは広告を返すことができます.

実装
JavaのStringBuilderは、文字列のコピーのオーバーヘッドの一部なしで繰り返し文字列連結の面倒を見ることができます.

JavaScriptコード
にジャンプします.Problem Description || Solution Idea )

const val = [1000,900,500,400,100,90,50,40,10,9,5,4,1]
const rom = ["M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"]

var intToRoman = function(N) {
    let ans = ""
    for (let i = 0; N; i++)
        while (N >= val[i]) ans += rom[i], N -= val[i]
    return ans
};

Pythonコード:
にジャンプします.Problem Description || Solution Idea )

val = [1000,900,500,400,100,90,50,40,10,9,5,4,1]
rom = ["M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"]

class Solution:
    def intToRoman(self, N: int) -> str:
        ans = ""
        for i in range(13):
            while N >= val[i]:
                ans += rom[i]
                N -= val[i]
        return ans

Javaコード:
にジャンプします.Problem Description || Solution Idea )

class Solution {
    final static int[] val = {1000,900,500,400,100,90,50,40,10,9,5,4,1};
    final static String[] rom = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};

    public String intToRoman(int N) {
        StringBuilder ans = new StringBuilder();
        for (int i = 0; N > 0; i++)
            while (N >= val[i]) {
                ans.append(rom[i]);
                N -= val[i];
            }
        return ans.toString();
    }
}

C++コード:
にジャンプします.Problem Description || Solution Idea )

class Solution {
public:
    const int val[13] = {1000,900,500,400,100,90,50,40,10,9,5,4,1};
    const string rom[13] = {"M","CM","D","CD","C","XC","L","XL","X","IX","V","IV","I"};

    string intToRoman(int N) {
        string ans = "";
        for (int i = 0; N; i++)
            while (N >= val[i]) ans += rom[i], N -= val[i];
        return ans;
    }
};