12. 整数转罗马数字(贪心！)

题目

12. 整数转罗马数字

我的思路

对十进制数字，从高位到低位逐个转换即可？

我的实现

class Solution {
public:
    string intToRoman(int num) {
        string result;
        while(num>=1000){
            num-=1000;
            result.push_back('M');
        }
        if(num>=900){
            num-=900;
            result.push_back('C');
            result.push_back('M');
        }else if(num>=400&&num<500){
            num-=400;
            result.push_back('C');
            result.push_back('D');
        }else if(num>=500){
            result.push_back('D');
            num=num-500;
        }
        while(num>=100){
                num-=100;
                result.push_back('C');
        }

        if(num>=90){
            num-=90;
            result.push_back('X');
            result.push_back('C');
        }else if(num>=40&&num<50){
            num-=40;
            result.push_back('X');
            result.push_back('L');
        }else if(num>=50){
            result.push_back('L');
            num=num-50;
        }
        while(num>=10){
                num-=10;
                result.push_back('X');
        }

        if(num>=9){
            num-=9;
            result.push_back('I');
            result.push_back('X');
        }else if(num>=4&&num<5){
            num-=4;
            result.push_back('I');
            result.push_back('V');
        }else if(num>=5){
            result.push_back('V');
            num=num-5;
        }
        while(num>=1){
                num-=1;
                result.push_back('I');
        }

        return result;

    }
};
/*
对十进制数字，从高位到低位逐个转换即可？
*/

拓展学习

其实可以观察转换规律，更简洁优美。贪心算法

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

        string res;
        int 
        for (int i = 0; i < 13; i ++ )  //这里不使用图里的count了，一遍一遍来就行了
            while(num >= values[i])
            {
                num -= values[i];
                res += reps[i];
            }
        return res;
    }
};

作者：z1m
链接：https://leetcode-cn.com/problems/integer-to-roman/solution/tan-xin-ha-xi-biao-tu-jie-by-ml-zimingmeng/
来源：力扣（LeetCode）
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