LeetCoder 12. Integer to Roman

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题意

将一个数字转换为罗马数字.
什么是罗马数字呢？就是我们钟表上面的时刻，例如：I,II,III,IV,V,VI,VII,VIII,IX,分别代表阿拉伯数字1−10

思路

关于罗马数字的规则和解释在这里：罗马数字
因为题目规定数字最大为3999，所以说，我们可以根据这个打一个表

M[] = {"", "M", "MM", "MMM"};C[] = {"", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"};X[] = {"", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"};I[] = {"", "I", "4II", "III", "IV", "V", "VI", "VII", "VIII", "IX"};

根据表进行组合即可.

结果

Your runtime beats 67.78 % of cpp submissions.

代码

class Solution {public:    string intToRoman(int num) {        string ans = "";        int cnt = num / 1000;        for(int i = 0; i < cnt;i++){            ans += "M";        }        num = num % 1000;        addRoman(100, num / 100, ans);        num = num % 100;        addRoman(10, num / 10, ans);        num = num %10;        addRoman(1, num, ans);        return ans;    }    void addRoman(int level, int cnt, string &ans){        string Left, Mid, Right;        if(level == 100){            Left = "C";            Mid = "D";            Right = "M";        } else if(level == 10){            Left = "X";            Mid = "L";            Right = "C";        } else{            Left = "I";            Mid = "V";            Right = "X";        }        if(cnt <= 3){            for(int i = 0; i < cnt;i++){                ans += Left;            }        } else if(cnt == 4){            ans = ans + Left + Mid;        } else if(cnt <= 8){            ans += Mid;            for(int i = 0;i < cnt - 5;i++){                ans += Left;            }        } else{            ans = ans + Left + Right;        }    }};

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