leetcode integer-to-roman

pynash123

于 2019-04-07 16:49:50 发布

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分类专栏： leetcode 算法

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本文介绍了一种将整数转换为罗马数字的算法实现，输入范围限制在1到3999之间。通过解析罗马数字的构成规律，采用递减匹配的方法，实现了从千位到个位的逐位转换。

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Given an integer, convert it to a roman numeral.
Input is guaranteed to be within the range from 1 to 3999.

I = 1;
V = 5
X = 10
L = 50
C = 100
D = 500
M = 1000

class Solution {
public:
    string intToRoman(int num) {
        string res = "";
        char roman[] = {'M', 'D', 'C', 'L', 'X', 'V', 'I'};
        int value[] = {1000, 500, 100, 50, 10, 5, 1};
        
        for (int n = 0; n < 7; n += 2) {
            int x = num / value[n];
            if (x < 4) {
                for (int i = 1; i <= x; ++i) res += roman[n];
            } else if (x == 4) res = res + roman[n] + roman[n - 1];
            else if (x > 4 && x < 9) {
                res += roman[n - 1];
                for (int i = 6; i <= x; ++i) res += roman[n];
            }
            else if (x == 9) res = res + roman[n] + roman[n - 2];
            num %= value[n];            
        }
        return res;
    }
};